Try on the pants and mark the desired hem length with pins or tailor’s chalk
Measure from the waistband seam down to the mark for both legs; confirm the same length
Turn the pants inside out
Fold the hem allowance up to your marked line and press lightly
Pin along the folded edge, keeping the fold even around the leg
Check the hem while wearing (or by measuring against the floor) and adjust if needed
Remove the pants and trim excess fabric, leaving enough for the hem allowance (typically 1–2 inches / 2.5–5 cm)
Finish the raw edge (zigzag stitch, serger, or overcast) to prevent fraying
Fold the hem up again to the final pressed line
Press the hem in place
Pin the hem again to secure it
Stitch the hem:
Hand sew with a blind hem stitch, or
Sew with a blind hem machine stitch, or
Use a straight stitch close to the folded edge if appropriate for the fabric
Remove pins and press the finished hem again
Repeat for the other leg, matching the hem height exactly
Press the final hem to set the stitches and ensure a clean finish