Things You'll Need
Don't spend money on new clothes or tailoring if your weight gain is a short-term condition. Whether you're trying to lose a little holiday weight or waiting on your baby bump to become full-grown, temporarily expand your waistline with a short strip of buttonhole elastic. Not only does the elastic allow you breathing room, but it can also be removed once you return to your regular size. If you aren't handy enough to sew your pants, a ponytail holder or elastic headband allows you to let out your waistline without a needle and thread.
Cut a piece of buttonhole elastic containing at least four buttonholes. Buttonhole elastic has one button hole per inch. Once sewn to the pants, this piece allows you to expand the waist by at least 3 inches. If you think you'll need more room later, cut more now.
Align 1 inch of the elastic on the inside of your waistband opposite your existing button. Pin it in place.
Secure the elastic to your waistband using the serge function on your sewing machine. Sew the free edge as well as the top and bottom.
Sew a button on the inside of your waistband on the opposite side if your pants don't have an existing button.
Thread a ponytail holder or rubber band through the buttonhole of your pants so you are holding a loop on either side. If you're pregnant and need more room, use an elastic headband.
Place the loop on the inside of the pants through the loop on the outside of the pants and pull tight.
Loop the free end over the button of your pants.