How is the shrinkage amount calculated?

I've had some things shrink lengthwise,

some crosswise,

and some things have shrunk both lengthwise and crosswise.

I'm fairly sure that is has something to do with the difference between the original size of the piece and the shrunken size -

but beyond that, I'm stuck.

For example - if I start out with a piece of fabric that is 36 x 42 before washing (1512 square inches) and after washing it would be 35 x 41 (1435) -> the difference is 77 inches.

77 divided by 1512 is approximately .0496 inches ->

to get from a decimal number to a percentage - I move the decimal two places to the right -> which would be 4.97% (rounded to two decimal places)

ETA: (MTS has the correct number - it should be 0.0509...)

So then would my shrinkage have been approximately 5% ??

Are the calculations the same if the shrinkage is only in one direction?