Things You'll Need
Attempting to wear a pair of pants with an inseam that is too short is a recipe for discomfort. An inseam that is too short can rub up too high, making sitting and walking uncomfortable for the wearer. A short inseam will also make your pants look like high waders. If you can't find an inseam that fits your measurements, you can lengthen an existing inseam in a pair of pants by dropping the hem and stitching a new one back onto the cuffs.
Unstitch the bottom hem of the pants with a seam ripper. Pull out all of the stitches so that you can drop the hem and release the additional fabric that is tucked under the pants cuffs. Unfold the hem.
Take the correct inseam measurements. Hold the sewing tape up the inside of the pant leg until one end of the tape reaches just below the crotch area. Pull the other end of the sewing tape to the correct length and take the measurement. Figure out the difference in inches. For instance, if the inseam was 32 inches and it needs to be lengthened to 34 inches, you need 2 inches of additional fabric to make the pants longer.
Cut a corresponding piece of fabric that matches the fabric of the garment you are lengthening. You only need to complete this step if you do not have enough fabric from the hem that is unfolded.
Create a new hem with a sewing machine. You can choose different methods for finishing the bottom, such as a controlled fray or simply sewing a straight stitch if that is easier.
Take the measurement of the new inseam, measuring with the sewing tape from just below the crotch to the ankle where the pants come down to. See if it is longer than the original length of the inseam.
Wash the pants in a washing machine. Do not put them in the dryer when the wash cycle is finished.
Grab the pants from end to end, with one hand on the waist and one hand on one pant leg. Begin to pull to stretch the material. This is known as damp stretching. Work your pull all along the pant leg so that the fabric and inseam stretches out.
Wait for the pants to dry -- don't dry in the dyer -- and try them on to see if the inseam is a little longer. Damp stretching is not intended for significant increases, but it can make small changes to an inseam.