Lay the pants flat on a smooth surface
Smooth out any wrinkles
Measure from the top of the waistband to the bottom hem for full length
For inseam, measure from the crotch seam to the bottom hem along the inner leg
For outseam, measure from the top of the waistband down the outer side to the hem
Keep the measuring tape straight and taut
Record the measurement in inches or centimeters
Double-check the measurement for accuracy