Put on the jeans and mark the desired length with chalk or a fabric pen
Remove the jeans and lay them flat on a table
Measure both legs to make sure the marks are even
Add extra length for hemming if you want a finished edge
Cut one leg at a time with sharp fabric scissors
Fold the shorts up to check the length and adjust if needed
Trim the second leg to match the first
Cut slightly longer than desired if you want frayed hems
Fold and sew the hem if you want a clean finish
Wash and dry the shorts to soften and fray the edges if desired