Shortening ready-to-wear pants at the hem sounds easy, but one needs to know some things. It’s good to know your stuff.
First, I must bring your attention to Mary A. Roehr’s book, published in 1987. Look beyond the hand drawing and the self-published look of the book and it is a treasure trove! I know, there are many, many slick alteration books and video content on the subject, but Mary was one of the earliest authors who focused on altering ready made clothing for home sewers. I learned a lot from her.
If your ready to wear pants are cut straight down from the knee or the hip, you can cut away the excess length (keeping enough fabric for the desired hem allowance inside), fold it up, press, stitch and you are on your way.
What if the pants are tapered? Well, just cutting off the desired length will yield this conundrum as in the image below. The circumference of your newly cut edge will be smaller than the pant leg circumference where you need to stitch down the new hem. Stretching it to sew the hem will result in awful, ugly puckers. Keep calm and read on.
Okay, so you’ve cut away the extra fabric for the hem (keeping the hem allowance); now turn up the hem to where you want it. Open up the side seams a little bit above the hem fold at the bottom until the two circumferences match up. Fold up and press the hem; then fold raw edges of the tiny V shape and tack them down to the pant seam allowances only – so that these stitches do not show on the right side. Finish the sewing the hem to puckerless beauty. The image below from the book referenced above, should explain it.
If you can’t stand to see that open V – well, no one will know it’s there but you’ll know. There’s a solution for that; remember the extra fabric we cut off to shorten the hem? Just cut out a triangular piece to fit under the V and discreetly sew it down to the V edges (not to the pant leg). Turn up the hem as usual. Be aware that this might result in a bit of bulk inside the hem. An alternative is to use a scrap of thin lining fabric in a matching color to “fill in” the V.
A final word to my fellow home seamstresses: do not hate alterations. There are tons of sewing tricks and methods I learned from taking apart good RTW clothing. I love to alter things; alteration is a cousin to refashioning and upcycling