How many times have you purchased the perfectly fitting pair of pants then after washing and drying, they are suddenly too short. Not only are they too short, you can’t lengthen the hem because there’s not enough hem in the first place.
Here’s one way to do it:
First thing to do is take out the hem using a sharp seem ripper. Then using water spray or steam, iron the pants as flat as you can. I used a piece of molding left over from a project as an iron clapper. This really helps to flatten the bump where the stitching used to be. The fold line at the bottom will become the lower edge of the pant leg.
Next I used a plain black Sharpie marker and gently drew over the line where the lower edge was. As you can see in the picture, the sharpie covers the line pretty good. I also used it on the old stitching line.
Using a wide, single fold bias tape, sew it to the pant just below the fold line of the new hem, overlapping a half inch where the beginning and end of the bias tape meet. Iron the bias tape down away from the pant leg.
Fold and press the hem up using the fold line of the new hem. You now have plenty of fabric in the hem (bias tape) to make a decent hem. Pin the bias tape in place so that you can sew directly on top of the sharpie-covered old hem line. I used a triple stitch to sew the new hem. You can also sew the new hem with a regular single stitch.
As you can see in the last picture, the pants turned out pretty good. And they are the perfect length for me. You have to get down and look closely to see that there was anything done to the hem. For myself, I don’t know anyone who would look that close.