why is the US not Metric

[forrestc]

The explanation that it costs a fortune to change is not convincing. If the US were an impoverished country, full of starving children, I'd agree with that argument.
But the fact is that the rest of the world converted to metric, proving that it is not so expensive, much less difficult, as the US claim.

I think you're still under the mistaken impression that the US hasn't adopted the metric system.   And also under the mistaken impression that all other countries have not only adopted the metric system but converted every last thing in their country to metric.

Just because the US has not seen fit to replace all of their street signs with metric, and still use degrees F does not mean that we've not adopted the metric system.

When I go to the doctor (in the US) I'm weighed in kilos and it's entered in the computer that way.   Yes, my scale at home still reads pounds, and most people know their weight in pounds instead of kilos, but that's because people are more familar with that scale.  But the medical profession uses kilos.  Note that other countries are similar.  For some reason in the UK, humans are weighed in stones....

Airbus still builds planes (in the EU) using inch hardware.

Automobiles built in the US use metric hardware pretty much exclusively.

De-facto standards are hard to replace.   The problem isn't the 'cost' to do it in the US.  It's the "cost/benefit" ratio.   And for things like our road signs and ambient temperature, I can pretty much guarantee that the amount of savings (i.e. benefit) to switching all of the signs from miles to km is pretty close to zero, with an enormous cost.    What is it *costing* the US to continue to use miles on our road system?   Well, maybe cars are a tiny bit more expensive because they have to have US instrument panels and metric instrument panels.   But since this is either a couple of lines of software (for a digital display) or a bit of printing difference, it's only going to be a tiny amount.   I can guarantee that the rest of the system (other than the display) is identical worldwide.    So there is little economic benefit to do so, for this example. 

Anywhere there is a strong economic benefit to do so, the conversion has been done.   And as technology marches on, things which are simpler when implemented in metric are going to get done that way.   And things (like the road signs) which don't end up saving us money, in the long run, won't be done.   Technology is actually making this divide wider - things which are done *inside* the technology are being done in metric, and the displays are staying in customary units because the cost to do so is marginal, even though the calculations under the surface is 100% metric.

[Cerebus]

For some reason in the UK, humans are weighed in stones....

Not universally true in the UK any more. Here, as probably everywhere, kilos are used by the medical profession and the man in the street seems more and more comfortable with expressing corporeality that way. I can tell you what I weight in kg, if I wanted to tell you in stone I'm have to convert via pounds. What you'll never heard a Brit saying is 'so-and-so weighs 180 lb'. Stone, by the way, is one of those peculiar units that doesn't take a plural - someone will say "9 stone 12 pounds" or just "9 stone 12", never "9 stones 12 pounds".

For those not familiar with the unit: 1 stone = 14 lb = ¹/₈ hundredweight = ~ 6.36 kg. A hundredweight  (112lb, ¹/₂₀ ton, ~ 50.9 kg) used to be the standard size for sacks of flour, coal and similar commodities - the amount a man could shoulder until the Europeans came along and told us that a man could only carry 25 kg on his own. 

[bsfeechannel]

I think you're still under the mistaken impression that the US hasn't adopted the metric system.

The US haven't. We can see by the replies in this forum that people are still attached to imperial units and won't let go of them.

And also under the mistaken impression that all other countries have not only adopted the metric system but converted every last thing in their country to metric.

The fact that you can find imperial nuts in metricated countries doesn't mean that those countries adopted imperial.

Just because the US has not seen fit to replace all of their street signs with metric, and still use degrees F does not mean that we've not adopted the metric system.

If the US have not seen fit to replace customary units with metric units, the US have not adopted metric.

When I go to the doctor (in the US) I'm weighed in kilos and it's entered in the computer that way.   Yes, my scale at home still reads pounds, and most people know their weight in pounds instead of kilos, but that's because people are more familar with that scale.  But the medical profession uses kilos.  Note that other countries are similar.  For some reason in the UK, humans are weighed in stones....

Airbus still builds planes (in the EU) using inch hardware.

Automobiles built in the US use metric hardware pretty much exclusively.

De-facto standards are hard to replace.   The problem isn't the 'cost' to do it in the US.  It's the "cost/benefit" ratio.   And for things like our road signs and ambient temperature, I can pretty much guarantee that the amount of savings (i.e. benefit) to switching all of the signs from miles to km is pretty close to zero, with an enormous cost.    What is it *costing* the US to continue to use miles on our road system?   Well, maybe cars are a tiny bit more expensive because they have to have US instrument panels and metric instrument panels.   But since this is either a couple of lines of software (for a digital display) or a bit of printing difference, it's only going to be a tiny amount.   I can guarantee that the rest of the system (other than the display) is identical worldwide.    So there is little economic benefit to do so, for this example. 

Anywhere there is a strong economic benefit to do so, the conversion has been done.   And as technology marches on, things which are simpler when implemented in metric are going to get done that way.   And things (like the road signs) which don't end up saving us money, in the long run, won't be done.   Technology is actually making this divide wider - things which are done *inside* the technology are being done in metric, and the displays are staying in customary units because the cost to do so is marginal, even though the calculations under the surface is 100% metric.

Either the cost is "enormous" or "marginal". Make up your mind. All road signs have to be replaced from time to time. If you were really willing to convert to metric, you would have already put a plan into action decades ago to gradually convert those signs and by now you wouldn't have to repeat those paradoxical explanations that no one buys.

As I said REPEATEDLY, all other nations have been successful in converting to metric generations ago (that's not a figure of speech). So there's no excuse.

[Cubdriver]

No one is making paradoxical explanations.  The question was posed - "Why is the US not metric?"  It has been answered repeatedly in this thread.  The fact that YOU refuse to accept that answer, and insist on arguing against what people here have told you over and over, does not make it wrong.

-Pat

[boffin]

For some reason in the UK, humans are weighed in stones....

Not universally true in the UK any more. Here, as probably everywhere, kilos are used by the medical profession and the man in the street seems more and more comfortable with expressing corporeality that way. I can tell you what I weight in kg, if I wanted to tell you in stone I'm have to convert via pounds. What you'll never heard a Brit saying is 'so-and-so weighs 180 lb'. Stone, by the way, is one of those peculiar units that doesn't take a plural - someone will say "9 stone 12 pounds" or just "9 stone 12", never "9 stones 12 pounds".

For those not familiar with the unit: 1 stone = 14 lb = ¹/₈ hundredweight = ~ 6.36 kg. A hundredweight  (112lb, ¹/₂₀ ton, ~ 50.9 kg) used to be the standard size for sacks of flour, coal and similar commodities - the amount a man could shoulder until the Europeans came along and told us that a man could only carry 25 kg on his own. 

Nice try, but not quite right. 

Most commodities (flour, potatoes etc) were distributed/sold by sacks of "HALF HUNDREDWEIGHT", or they certainly were when my family owned a store in the UK in the 70s.
and 25kg is almost exactly a 'half-hundredweight".  But nice try on blaming the Europeans for something with incorrect information, I assume you think the EU tried to ban bananas as well.

[bsfeechannel]

No one is making paradoxical explanations.  The question was posed - "Why is the US not metric?"  It has been answered repeatedly in this thread.  The fact that YOU refuse to accept that answer, and insist on arguing against what people here have told you over and over, does not make it wrong.

-Pat

Of course I don't accept it. It contains contradictions. The cost of switching to metric is in fact marginal. And the benefits enormous. If that weren't true, the world wouldn't have taken the plunge.

By the way. Let's take this opportunity to do something I don't recall anyone doing. The metric system is one of the greatest gifts from the French to the whole world. It really helps our everyday lives. It simplifies things, eliminates ambiguities, lower costs. It is logic, systematic, consistent. It is good for the woodworker, the cook, the shopkeeper, the engineer, the scientist.

It is free and you don't get lectured about going to the moon, Uranus or some place where the sun doesn't shine, every time you use it.

So, I guess  I can say this in the name of the whole world: thank you, France.

Le jour de gloire est arrivé!

P.S.: Meanwhile we could organize a whip-round to help the US replace their road signs. If everyone on the planet chips in $1, I think we could metricate the road from El Paso all the way to Las Cruces.

[SiliconWizard]

It is free and you don't get lectured about going to the moon, Uranus or some place where the sun doesn't shine, every time you use it.

Ahah, I liked this one.

[Cerebus]

For some reason in the UK, humans are weighed in stones....

Not universally true in the UK any more. Here, as probably everywhere, kilos are used by the medical profession and the man in the street seems more and more comfortable with expressing corporeality that way. I can tell you what I weight in kg, if I wanted to tell you in stone I'm have to convert via pounds. What you'll never heard a Brit saying is 'so-and-so weighs 180 lb'. Stone, by the way, is one of those peculiar units that doesn't take a plural - someone will say "9 stone 12 pounds" or just "9 stone 12", never "9 stones 12 pounds".

For those not familiar with the unit: 1 stone = 14 lb = ¹/₈ hundredweight = ~ 6.36 kg. A hundredweight  (112lb, ¹/₂₀ ton, ~ 50.9 kg) used to be the standard size for sacks of flour, coal and similar commodities - the amount a man could shoulder until the Europeans came along and told us that a man could only carry 25 kg on his own. 

Nice try, but not quite right. 

Most commodities (flour, potatoes etc) were distributed/sold by sacks of "HALF HUNDREDWEIGHT", or they certainly were when my family owned a store in the UK in the 70s.
and 25kg is almost exactly a 'half-hundredweight".  But nice try on blaming the Europeans for something with incorrect information, I assume you think the EU tried to ban bananas as well.

No, the EU didn't try to ban bananas. Unfortunately neither did the EU require us to re-educate people who were too dim to spot a joke, even when it's got a sodding smiley next to it, before we permitted them to emigrate.

Anyway, I didn't say all commodities under all circumstances came in hundredweight sacks, but the coalman definitely delivered coal in them, and it was the standard size for most things used in industrial quantities like flour by bakers. Obviously things used in relatively small quantities by small traders, or if they were perishable, or had a shortish shelf life, came in smaller quantities e.g. potatoes, onions, carrots, and so on tended to come in 56 lb sacks.

[Sal Ammoniac]

I don't see why people from other countries are so concerned about what measurement standards we use in the U.S. If you like the metric system, fine, use it, but don't try to force your opinions on everyone else (only we're allowed to do that  ). In any case, U.S. manufacturers will ultimately use whatever system the market demands (and already do, for the most part).

[GeorgeOfTheJungle]

(only we're allowed to do that  )

  LOL  

[Zero999]

The explanation that it costs a fortune to change is not convincing. If the US were an impoverished country, full of starving children, I'd agree with that argument.
But the fact is that the rest of the world converted to metric, proving that it is not so expensive, much less difficult, as the US claim.

I think you're still under the mistaken impression that the US hasn't adopted the metric system.   And also under the mistaken impression that all other countries have not only adopted the metric system but converted every last thing in their country to metric.

Just because the US has not seen fit to replace all of their street signs with metric, and still use degrees F does not mean that we've not adopted the metric system.

When I go to the doctor (in the US) I'm weighed in kilos and it's entered in the computer that way.   Yes, my scale at home still reads pounds, and most people know their weight in pounds instead of kilos, but that's because people are more familar with that scale.  But the medical profession uses kilos.  Note that other countries are similar.  For some reason in the UK, humans are weighed in stones....

Airbus still builds planes (in the EU) using inch hardware.

Automobiles built in the US use metric hardware pretty much exclusively.

De-facto standards are hard to replace.   The problem isn't the 'cost' to do it in the US.  It's the "cost/benefit" ratio.   And for things like our road signs and ambient temperature, I can pretty much guarantee that the amount of savings (i.e. benefit) to switching all of the signs from miles to km is pretty close to zero, with an enormous cost.    What is it *costing* the US to continue to use miles on our road system?   Well, maybe cars are a tiny bit more expensive because they have to have US instrument panels and metric instrument panels.   But since this is either a couple of lines of software (for a digital display) or a bit of printing difference, it's only going to be a tiny amount.   I can guarantee that the rest of the system (other than the display) is identical worldwide.    So there is little economic benefit to do so, for this example. 

Anywhere there is a strong economic benefit to do so, the conversion has been done.   And as technology marches on, things which are simpler when implemented in metric are going to get done that way.   And things (like the road signs) which don't end up saving us money, in the long run, won't be done.   Technology is actually making this divide wider - things which are done *inside* the technology are being done in metric, and the displays are staying in customary units because the cost to do so is marginal, even though the calculations under the surface is 100% metric.

Yes, I agree. Also note that in electronic systems, quite often, neither metric nor imperial/customary are used internally. For example, in a weighing machine, a strain gauge will output a voltage per Newton, which is sampled by an ADC, giving X number of counts/Newton, which is converted to metric or imperial/customary for the user. In precision applications, the local gravitational constant will be used, by calibrating it where ever it's going to be used, with a standard mass.

Either the cost is "enormous" or "marginal". Make up your mind. All road signs have to be replaced from time to time. If you were really willing to convert to metric, you would have already put a plan into action decades ago to gradually convert those signs and by now you wouldn't have to repeat those paradoxical explanations that no one buys.

Some things are cheap to convert to metric, others are very expensive. Road sings fall into the expensive category. It's not safe to replace road signs on an ad-hock basis, especially speed limits, because it would confuse drivers. All road signs would need to be replaced in one go, at great expense. There would be little benefit in converting to metric because no one is performing calculations in feet, yards and miles. There is only one unit: miles per hour and it's no easier to use km per hour or even metres per second, which is the true SI unit for velocity.

Changing units on food packaging to metric and insisting commodities are primally sold in metric would be fairly cheap and would have some benefit, but I suspect this is already the case to some degree. I wouldn't be surprised if metric is already found on US food packets, as they export them to metric countries such as Canada and Mexico.

[bsfeechannel]

It is free and you don't get lectured about going to the moon, Uranus or some place where the sun doesn't shine, every time you use it.

Ahah, I liked this one.

Finally someone with some sense of humor. 

[bsfeechannel]

Some things are cheap to convert to metric, others are very expensive. Road sings fall into the expensive category.

If everyone in the world contributed with just $1 for the US metrication cost, we would have $7.4B. Do you think that with that money we could change the US road signs?

If the answer is yes, shut up and take my money.

[tpowell1830]

I don't see why people from other countries are so concerned about what measurement standards we use in the U.S. If you like the metric system, fine, use it, but don't try to force your opinions on everyone else (only we're allowed to do that  ). In any case, U.S. manufacturers will ultimately use whatever system the market demands (and already do, for the most part).

Yes, I believe that everyone is entitled to an opinion, no matter how wrong they are... 

[KL27x]

Zero999:

As I said before, it's not so much the different bases which make imperial/customary difficult, but the fact that mass, length, volume are totally different systems. Metric is all one standard international system, with everything being multiples of powers of 10.

Example: we have a cuboid shaped fish tank, 4ft 6in long, 18in wide and 15in high. Calculate how many US gallons of water required to fill it to fill it to a depth of 1ft. I wouldn't have a clue how to figure it out using purely customary units. I'd just convert everything to metric:

So you know how to convert liters into gallons, but you can't figure out how to convert cubic feet into gallons?

We have internet. We don't have to go to the library of congress to look up either.

And if you can convert L and gallons, you can convert gallons and cubic meters. So you have already all you need without looking up anything.

If you want to say, no, I will leave answer in liters, ok. You can leave answer in cubic inches or feet, too. You said gallons.

Scary part is where you say you have no clue. This is evidence we must keep imperial as IQ test for engineer. Half the fuss is people angry over standardized tests. In real world, you do not have this problem. People who do actually do things don't care. People who take test and sit in front of computer and don't even use unit other than to read how many mL in their consumer face cream somehow care.

[SiliconWizard]

You mean US gallon, US dry gallon or imperial gallon? 

[boffin]

You mean US gallon, US dry gallon or imperial gallon? 

The correct answer for an American is likely "Freedom Gallons".

[Zero999]

Zero999:

As I said before, it's not so much the different bases which make imperial/customary difficult, but the fact that mass, length, volume are totally different systems. Metric is all one standard international system, with everything being multiples of powers of 10.

Example: we have a cuboid shaped fish tank, 4ft 6in long, 18in wide and 15in high. Calculate how many US gallons of water required to fill it to fill it to a depth of 1ft. I wouldn't have a clue how to figure it out using purely customary units. I'd just convert everything to metric:

So you know how to convert liters into gallons, but you can't figure out how to convert cubic feet into gallons?

We have internet. We don't have to go to the library of congress to look up either.

I don't need the Internet. I performed that calculation, without looking anything up. I can remember the metric to the most commonly used imperial/customary conversions easily. I don't need to convert cubic inches to gallons. I just remember 1 US pint = 473ml and 1 imperial pint = 568ml. Nowadays it's necessary to be able to convert between metric and imperial/customary anyway,  so there's little point in remembering things such as cubic inches to pints, the mass of a gallon of water, etc. just convert it all to metric, then it becomes easy.

[KL27x]

Wow, freedom gallons. So many metric trolls. I think the metric trolls added up in this thread convert to 4.6 rstophers, imperial unit of troll. Conversion is 1 rstopher: 1.108 bsfeechannel.

Zero, you could also do the calculation in imperial all the way to cubic feet, then convert to cubic decimeters. Then convert L to gallons. At least if you do in cubic feet, you have that original parameter of 1 foot high vs 308.4mm. You do just ONE conversion to get Liters. You don't have to do extra conversion of all dimensions of the tank to metric, doing 3 extra steps vs 1.

The reason you convert all distances to metric is maybe you are more comfortable to think in metric? Americans think in imperial. That's your internal calibration, and it is probably not going to ever change. Same can be said about americans. We know what is 1.5m, but we don't intrinsically know if that is Tom Cruise or James Harden height. (Ok, I know it's way closer to Tom Cruise. But Tom Cruise or Kevin Hart? Getting tougher..)

When performing a calculation like your example, anyway you do it should be equally comfortable. I don't get unit loyalty.

[forrestc]

Either the cost is "enormous" or "marginal". Make up your mind. All road signs have to be replaced from time to time. If you were really willing to convert to metric, you would have already put a plan into action decades ago to gradually convert those signs and by now you wouldn't have to repeat those paradoxical explanations that no one buys.

You've still missed the point:

What is the exact economic benefit of changing the units we measure our roads by from miles to km?   

I understand that you believe that you can just start replacing signs as they wear out with km versions.   Considering signs can and do last up to 30 years, this would take 30 years, during which time a certain percentage of the signs would be in KM and a certain percentage would be in miles.   Oh, so maybe we replace with signs with both systems, then at some point where most of the signs have been replaced switch to 'only km' versions.   That could take 50 years or more.

So the correct method is to replace big chunks all at once.   Which is very costly.  Let's just take speed limit signs.   There are 4.2 million miles of roads in the US.  I found a news article where a state changed their speed limit and replaced their speed limit signs at a cost of $134,000 for 810 miles of interstate.   Let's just assume that's a good ratio.   $134,000 for 810 miles.   $165 per mile, multipled by 4.2 million miles, is just under 700 million dollars just for the speed limit signs.   Then add in the much more expensive direction signs, distance signs, the mile markers along the road and on and on, and you are probably talking at least few billion dollars to just change the signage.

Not to mention all of the side effects of this change.   If you look at news articles about Interstate 17 in Arizona, you'll find lots and lots of people not happy about it being changed (eventually) back to miles because of the costs of the side effects (changing exit numbers, directions, etc, on printed material, and other costs).

And again, for what economic benefit?   Show us how we're going to save a few billion dollars by doing this and it will probably get done.   But as it is now, most people don't see a good reason to change this particular thing.   I get into my car, I look at the speedometer I make sure it doesn't exceed (by very much) the posted speed limit.   The distance signs also need to be in the same units since I just take the distance to the destination and divide by the current speed.   It doesn't matter what the number system is, as long as everything matches.   The distance could be miles, or kilometers, or furlongs or kilosmoots, it wouldn't matter.   I'm not doing engineering with those figures, and in this case there are a lot of costs to do the change, for no real benefit.

It's really frustrating to hear people say "the US isn't metric".   No, the US is metric, all of our units are defined in ratio to the metric unit, and every day more and more of the places where traditional measurements have been used are being replaced by metric measurements.   All to point at our highway system which doesn't really matter what units it's measured in.   

[CatalinaWOW]

If it bothers you that much, feel free not to come here and not to use anything we currently make that isn't based on a metric standard.

Too late.

And here we have the heart of the problem.  While the cost of replacing all of the non-metric street signs in America is trivial, the cost of replacing his brain dead, useless, totally antiquated US sourced products that he bought with beautiful metricated products, or the cost of moving back to some enlightened, forward thinking, economically advantaged part of the world is totally unreasonable.

Pardon me while I shed crocodile tears.

[tooki]

Changing units on food packaging to metric and insisting commodities are primally sold in metric would be fairly cheap and would have some benefit, but I suspect this is already the case to some degree. I wouldn't be surprised if metric is already found on US food packets, as they export them to metric countries such as Canada and Mexico.

Groceries in USA have been labeled with metric (with or without customary alongside it) for at least 30 years now, and metric has been required by law since 1992. The only things without even a metric conversion are things sold by variable weight that are weighed in-store (fresh meat, produce, etc), which will be in lbs (usually with decimals, but sometimes with ounces), and the same with items dispensed in-store by volume.

Similarly, when I was a little kid in USA, product packaging (both food and otherwise) was usually in English only, occasionally with French as well for products sold in Canada, too. But nowadays, practically everything is in English and Spanish, and frequently French as well. (I, for one, like that. Passive language instruction FTW!)

[KL27x]

Zero, I calculate for you. The cube root distance of a gallon is 6.136 inches. So a (freedom) gallon is a cube 6.136" per side, or 0.5113 feet, or 155.9mm.

This may be easier to use than mL:pint.

Of course when the numbers get so big or small they are not really relate-able, engineers commonly use cubic feet, or cubic meters or other stuff that is not a liter or a gallon.

Why this 6.136" number is not commonly known? We don't make square measuring cups. We don't make square swimming pools. We don't make square gas tanks.

[vk6zgo]

For those who abhor non-decimal factors in units, why do you put up with our current system of time?  Short of tweaking Earth's orbit, we can't do much about the number of days in the year, but all the subdivisions of a day are entirely up to us to control.   We don't need to follow the Babylonian system of 24, 60, and 60.  We could use centidays and millidays for ordinary timekeeping.  A centiday is 14.4 of our traditional minutes, and a milliday is 1.44 minutes.  Once we made the switch, we'd easily change our habits to make classes, meetings, and TV programs last two to four centidays, cookies bake in one centiday or a bit less, a work day is 33 centidays, etc.

Yes time is annoying, but we're stuck with the current definition of the second, which is an SI unit and there are 86.4ks per day, whatever we do. As mentioned above, if we change the second, we have to alter all of the other SI units which depend on it, such as capacitance.

As I said before, it's not so much the different bases which make imperial/customary difficult, but the fact that mass, length, volume are totally different systems. Metric is all one standard international system, with everything being multiples of powers of 10.

Example: we have a cuboid shaped fish tank, 4ft 6in long, 18in wide and 15in high. Calculate how many US gallons of water required to fill it to fill it to a depth of 1ft. I wouldn't have a clue how to figure it out using purely customary units. I'd just convert everything to metric:

An inch = 2.54cm and there are 12 of them in a foot.
l = (4*12+6)*2.54 = 137.16cm
w = 18*2.54 = 45.72cm
d = 12*2.54 = 30.48cm

well, the cubic capacity in cubic ft  of the tank is 4.5ft x 1.5ft x 1.25ft.
That isn't what we need though------the water level is only 1.0 ft, so the calculation simplifies to :-
4.5 x 1.5 x 1.0, or 4.5 x 1.5 for a cubic capacity of 6.75 cubic ft.

That's the easy part.
I haven't a clue what the conversion factor between cu ft & US Gallons is.
If I knew that, the whole thing would be done with two calculations. (with the values given, converting to decimal feet is obvious)

Back in the Imperial days, decimal parts of a foot, or whatever, were very commonly used, & well known.

A litre is 1000cm³
v = 137.16*45.72*30.48 = 191139cm³ = 191.1L

A US pint is 0.473L and there are 8 of them to the gallon.
191.1/0.473 = 404pt
404/8 = 50.5 so the answer is 50 gallons and 4 pints.

How much does does the water in the tank weigh, under standard conditions?
A litre of water near enough weighs 1kg, so 191.1kg. Oh, then answer needs to be in pounds and ounces?
1lb = 0.454kg
191.1/0.454 = 420.925lb
There are 16 ounces per pound:
0.925*16 = 14.8oz
So 420lb 14.8oz but 421lb is close enough.

I hope I've got that right!

There are conversions from cubic inches to pints and the density of a pint of water, but why bother? It's much easier just to memorise the imperial to metric conversions, which will come in handy sooner or later anyway.

[forrestc]

well, the cubic capacity in cubic ft  of the tank is 4.5ft x 1.5ft x 1.25ft.
That isn't what we need though------the water level is only 1.0 ft, so the calculation simplifies to :-
4.5 x 1.5 x 1.0, or 4.5 x 1.5 for a cubic capacity of 6.75 cubic ft.

That's the easy part.
I haven't a clue what the conversion factor between cu ft & US Gallons is.
If I knew that, the whole thing would be done with two calculations. (with the values given, converting to decimal feet is obvious)

Entering the following into google:

4'6" x 18" x 12" in gallons

Results in the following result:

(4 ' 6 ") x (18 ") x (12 ") =
50.4935065 US gallons

Doesn't get much easier than that