Soak the jeans in lukewarm water
Put the damp jeans on and stretch them by hand
Wear the jeans while they dry to help them expand
Use a spray bottle to dampen tight areas and pull gently
Insert a pants stretcher or waistband extender
Lay the jeans flat and pull on the waistband, thighs, and calves
Repeat stretching after each wash
Add fabric panels or gussets for a permanent size increase
Let out the side seams or center seam if there is enough seam allowance
Take the jeans to a tailor for professional alteration