How to Alter a Pair of Pants. When you have a pair of pants that don't fit right, you usually don't wear them. Since many people don't throw them away either, there they sit. Whether your pants are just not your size anymore or hand-me-downs, a few simple alterations can bring new life to that old clothing.
Decide what needs to change. If your pants are too short or too loose, the alterations are easy. If you need to add length or expand the legs, the alterations are a little more tricky. If there's no fabric to let out, simple alterations won't be possible.
Decide how much to take in or let out. If you are going to alter the length, rip out the seam at the bottom of the legs. Put the pants on and mark where you would like the pants to end. If you want to change the pants through the waist or hip area, put the pants on inside out. Pull at the seam in the back to determine how much to change. The same goes if you need to change the legs.
Iron and pin your desired seams. Though this step can seem like a waste of time, it gives you more professional looking results.
Sew your seams loosely and try on the pants for size. If you need to make more adjustments, tear out the seam and repeat Steps 2 and 3 until you have the fit you want.
Sew again. This time, use a tighter stitch. This will keep the pants together and finish off the alterations.