I had some old boot cut jeans that aren't my style, and I found myself never wearing them. It turns out to be super simple to transform them into skinny jeans! I wouldn't try this on your nicest pair of jeans for the first try, but it's definitely a way to salvage pants that were no longer getting any love.
Step 1: Put on Your Jeans Inside Out
1 Pull the excess fabric toward the outside of your leg.
2 Starting at your knee and progressing down the leg, use pins to section off the excess fabric
3 Both legs should look something like this
Step 3: Flatten Your Jeans
4 Carefully take off your jeans (remember, they have pins in them!)
5 If you like, overlay a pair of your existing skinny jeans just to make sure your pins roughly make a similar silhouette. This isn't strictly necessary, it's just a nice check. If you notice here, my pins are creating a leg shape slightly larger than my existing jeans, but that's OK. I'd rather start out too big than too small.
6 Working from the outside of the leg inward, press out any wrinkles. You may have to re-position a few pins, but you want to make sure that your upcoming seam isn't going to create any awkward transitional bumps.
Step 4: Draw in Sewing Guidelines
7 Use a ruler to create a straight line that follows your pins. At some point, the ruler should intersect with the jeans' existing seam. It's OK if the ruler doesn't touch every pin, but you want to make sure that the lines you are about to draw will approximate where you pinned.
8 I taped together a pen and a sharpie so that I can easily see my drawn lines. The purple line won't show up very well, but you only really need to see the black one. Taping the two together creates a dark line for the outside of your sewing machine's foot to follow.
9 Trace a straight line from the ruler with the lighter pen. The black line will be offset from the purple line about 5/8".
10 Your jeans should look something like this
Step 5: Sew the Sides of the Legs
11 Line up the outside of the sewing machine foot with the black line (as seen in the photo) and sew down the side of the leg. Your machine should be stitching along the purple line and along the pinned line. Remove the pins as you go.
12 Because I wear skinny jeans at ankle length, I also want to take the hem on the bottom of these flares up about 1.5". If you want to shorten the jeans, end your stitch about 1.5" above the bottom of the jeans and lock the thread by completing a few stitches in reverse. If you don't want to shorten the jeans, just keep stitching all the way to the bottom of the jeans and lock the stitch on the cuff.
Step 6: Remove Excess Material
13 Try on your jeans. If they are the correct width - awesome! If not, keep bringing the leg in with additional stitch rows. In this image, I am using the previous stitch line as the guide for the outside of my machine's foot to bring in the jeans an additional 5/8"
14 When you are happy with the leg width, trim off the extra material on the other side of the stitch
15 Hopefully, the pieces you cut off of both legs will be similar in shape.
Step 7: Begin Your New Hem Line
16 If you're happy with the jeans' width, you're ready to rock your new jeans. If you want to shorten the length, trim off excess fabric from the ends of the legs. For me, I wanted my jeans about 1.5" shorter, so I trimmed about 3/4" off (which coincidentally was the length of the existing hem)
17 The bottom of your legs will look like this.
18 Create a 1/2" cuff at the bottom of the jeans and iron it into place
19 Fold the cuff over one more time and flatten it with the iron
Step 8: Sew Your New Hem
20 Remove the extra table from your machine if you have one. This will make it easier to fit the small cuff of the jean onto the machine.
21 Sew around the cuff, using the bottom edge of the cuff as a guide for the outside of your zipper foot
22 Be careful where the side seam meets the cuff. The area is extra thick from all the layers of material, so sew slowly. I hand turned the needle instead of using the pedal to avoid any problems or broken needles.
Step 9: Finished!
Lay your jeans on the floor, make sure they look normal and even, and then try them on.
You're ready to rock your "new" jeans!