Wear fitted pants or shorts, or measure directly on bare legs
Stand straight with your feet about shoulder-width apart
Place a tape measure at the top of your inner thigh, where the leg meets the crotch
Run the tape measure straight down the inside of your leg to the bottom of your ankle
Keep the tape snug but not tight
Read the measurement in inches or centimeters
For more accuracy, have someone else measure for you
Compare the result to the inseam size listed on clothing or size charts