Here’s a method I used to take in a too big jeans waist when I worked as an alterations shop seamstress. Ready to save yourself $25? Gather those supplies!
Big fat heavy duty safety pin
Sewing machine needle (I used a universal 90 needle; size 100 or a special denim needle might be better for a heavier denim)
Tool to rip seams (I used my thread snips, but a seam ripper is totally acceptable)
Marking chalk (I prefer a wax tailor’s chalk)
Hammer or rubber mallet
All-purpose thread (we will use this for everything except topstitching)
Topstitching thread (find a thread that matches the stitching on the waistband, belt loops, and center back seam of your jeans; jeans/denim thread is your first choice, then heavy-duty, then all-purpose. See tips for success at the end of the tutorial for more information)
Step One: Pin
Put on your jeans and pin the center back seam so that your center topstitching falls to one side. Pull the waistband snug and secure the excess with an extra-large safety pin. Continue to pinch out the excess fabric down the center back seam until there’s no more excess left to pin. It may be easier to have another person do this step for you. Whoever pins–be careful not to pin your underwear!
Take off your jeans and put on some other pants (or don’t…I don’t!). Carefully mark along the pinned seam on the inside of the jeans. Remove pins. Don’t freak out, but it’s time to take them apart.
Step Two: Rip
Clip each line of waistband stitching a half inch or so outside of your markings. Jeans are usually sewn with a chain stitch, so be sure to clip the beginning and end of each stitchline you wish to remove. Trust me, pulling out chain stitching is really fun, but you don’t want to get too carried away! Go ahead and remove that section of stitching now.
Remove belt loop(s) at center back. With the interior chain stitches removed, you can clip away the corresponding thread on the outside of the waistband.
Separate the outer and inner waistband by clipping the stitches at the top of the waistband until you reach your intact chain stitches.
Measure the distance between your waistband markings. Memorize it (or just write it down I guess).
Clip the chain stitching an inch or so below the end of your center back seam markings. Pull from the top to remove chain stitching, and remove corresponding exterior thread.
Step Three: Sew
Well, not just yet. Pull out the waistband marking distance measurement from earlier. I had you pin your jeans so that all the topstitching was to one side because it is was easier and much more accurate than folding between the stitch lines. In order to hide the new waistband seam beneath your belt loop, we need to shift the center of the waistband markings so that it lies exactly between the topstitching lines instead of to one side.
Above you can see my original waistband markings (where the pins are). In my case, the pins are 2.5″ apart. SO, to be truly centered, I must shift them to the right so that each pin is 1.25″ from the middle of the old center back stitch lines. I don’t bother with actually marking new lines. Instead, I mark a line on the waistband at the true center and then fold the inner waistband on that line, right sides together.
Sew your inner waistband with a seam allowance of half your marking distance measurement. For me, this is 1.25″. This is really tight quarters for sewing, so I like the pin my desired stitch line and then mark with chalk so I have a visual to sew along.
Sew, trim (there’s not going back now!), press seam allowance open, turn out and admire.
Take in the outer waistband, using the inner waistband as a guide. Sew, trim, press, turn.
Now for the seat. Normally I would pin perpendicular to where I plan to sew, but not for this. Pin right sides together, all along your markings from earlier. Turn to the other side to make sure your pins are going through the markings on that side, too.
You’ll begin sewing right in the old fold line (where I’m pointing) and curve out, following your pins/markings. You may need to unpick a bit further down to avoid too sharp a transition. Use your hammer to pound the yoke seam you’ll be sewing across. There’s, what?, eight layers of denim there–so even a little bit of flattening will help. Sew slowly over this area–try to get those seams lined up as perfectly as possible.
Sew. This is a good time to try your jeans on and make sure there are no funny looking lumps or bumps in your new seat seam. If there are (for me–there usually are), go back and re-do the area that needs work. You can also adjust to better match the yoke seams.
Once you’re happy with the fit of your jeans, serge the excess off (leave enough to accommodate new topstitching–about a half inch). Turn right side out and give your new seat seam a nice press. Hammer at that yoke/seat seam intersection again. You’ll be topstitching through twelve or so layers this time.
Step Four: Finish
Switch to your matching topstitching thread. You can leave all-purpose thread in the bobbin. Sew each line of topstitching from the bottom up, overlapping a few stitches with the old stitch line.
Clip any loose threads on the waistband and then topstitch–don’t forget to hammer out the thick parts. Reattach the belt loop (hammer, hammer, hammer).
Put your pants back on and Check. Yourself. Out.
You did it! For an even better finish, try some of the tips below:
TIPS FOR SUCCESS:
Really pin as far down the seat as you can. The further down you go, the less noticeable the transition from original thread to DIY topstitching will be.
Use denim/jeans thread as a first choice. My local shop only had blue in stock, so I found a matching heavy duty thread. If you must use all-purpose thread for a good color match, try running two threads through your needle for a chunkier (more original looking) topstitch. Simply wind two bobbins of thread and place both on your vertical spool pin.
For unusual thread colors, try running two different color threads through your needle. I’ve had good success matching chunky “white” thread by using a heavy weight white or off-white thread with a light blue thread.
Make sure all your new topstitching overlaps the old the secure the chain stitch ends.
If your jeans are very worn along the seat seam, go at your new seam with a nail file to roughen it up. Be careful of your stitches, though!
Don’t attempt this alteration with your *favorite* jeans until you’ve got a few pair under your belt.
Don’t attempt this alteration after wearing your jeans all day, either. You want to do this to a pair of jeans fresh out of the dryer (or off the line… you get me?).
When removing the belt loop, clip the threads between the waist band and belt loop. Do NOT pick the threads from the belt loop. When you reattach later, just sew over the original thread still left in the belt loop. This will help disguise your alteration. Trust me.
What are you waiting for? Take off your pants and lose The Gap for good!