Another trick to help you measure is to tape a yardstick to the corner of a wall or doorframe.
Then stand sideways to it and touch the yardstick at where you want the top of the waistband to sit. Write down the number.



Then lean down and do the same at where you want the hem to hit. Write down this number.



Then simply subtract the hem reading from the waist reading and voila, drop.

This is how we at Freedom Kilts do it and how we ask our customers to measure themselves.