Resistor Tolerance

[Labrat101]

Personally when I am doing calibration if i have a say 1k with a rating of 1% . and measures
995.0250    I will add a 5 and lengthen or shorten the wires until it within 0.004%  .
 Resistance wire is also handy to have for supper fine.
I have just recalibrated a pro decade resistance box to within 0.4 per 1 meg .
Example ::
On cheap resistors just adding the loss .  example 100k @ 1% could be out by as much as 900
so adding what is the nearest value in your box 820 would bring it within a less than 1% good enough
for most hobbyists .
 

In real life I am using MIL grade equipment only