Sew Pants: Convert a Basic Pattern into Sweatpants

by SaraD on May 4, 2011

One of the reasons I sew is that I have a hard time finding clothes that fit. The last time I bought sweatpants, I ended up in the men’s department and still had to piece in some extra fabric to make the legs long enough. Now those sweatpants are coming apart, so I decided to make my own. It couldn’t be all that hard.

Adapt a pants pattern

Pattern adjustments for sweatpants

Pattern adjustments for sweatpants (click for larger image).

I used a basic pants pattern that had been fitted for me a couple years ago. It had darts in the front and back and straight legs–a good basic foundation. Here’s how to adapt such a pattern for sweatpants:

  1. Straighten out the side seams from the hip to the waist to convert the pattern into pull-on pants.
  2. Don’t sew the darts.
  3. Add an extension to the top of the front and back to form a casing for the elastic. In this case I added 2 1/2″:
    Elastic 1 1/4″
    Seam allowance 5/8″
    Fitting allowance 5/8″
    Total 2 1/2″
  4. Narrow the pant leg to suit your taste. Starting just below the crotch, angle both the side seam and the inseam in toward hem by the amount desired. I narrowed mine by 4″, taking in 1″ from each seam (front and back).
  5. If you want inseam pockets, add a 3/4″ extension to the side seams from the top of the front and back to about 10″ below the waist. I used a pocket pattern from another pants pattern.
  6. If you want to add ribbing cuffs, cut two strips of ribbing the desired length (height) and wide enough to slide over your foot and ankle. For my pants, I used:
    Length Width
    finished length (height) 3 1/2″ finished width 12”
    x2 3 1/2” seam allowance 5/8″
    seam allowance 5/8”
    Total Length* 7 5/8” Total width 12 5/8

    *lengthwise grain of ribbing

Construct the pants

I constructed the sweatpants the same as for regular pants. Because I wasn’t quite sure of the fit, I stitched the inseams and the crotch seam, then pinned the side seams and tried on the pants. When I was satisfied the fit was right, I marked the waistline with chalk. Then I proceeded with the pockets and side seams:

  1. Stitch the pocket pieces to the extensions on the front and back (line up the top of the pocket with the waistline (marked in chalk).
  2. Pin the front and back together (right sides together) at the side seam.
  3. Pin mark the pocket opening. The opening is 6″, so place pins at:
    • 1 7//8″ below waistline
    • 7 7/8″ below waistline
  4. Stitch the side seams:
    1. Stitch from the top to the top of the pocket opening. Backstitch to lock the seam.
    2. Lift your presser foot and skip to the bottom of the pocket opening. Backstitch to lock the seam and continue stitching to the hem.
  5. Stitch the pocket pieces together, meeting up with side seam at pocket openings. Optional: serge the seam allowances (pocket & side seam) to finish the edges.

Create an elastic waistband

    Waistband casing

    Fold at waistline and stitch to form casing.

  1. Baste the front edges of the pockets to the pants from top to 1 1/2″ from top to keep the pockets flat when you feed the elastic through the casing.
  2. Fold over the top of the pants at the waistline.
  3. Starting near center back, stitch 1 1/2″ from folded edge to form a casing for elastic.
    • Leave a 2″ opening at center back.
    • Use a “baby zigzag” for stretch (1mm wide by 3mm long). Or, if your machine has a stretch stitch, you can experiment with it and see what works for you.
    • This casing is for 1 1/4″ elastic. If your elastic is narrower, you can narrow the casing, just make it 1/8″ wider than your elastic.
  4. Trim the seam allowance but don’t trim the seam allowance of the 2″ opening.
  5. Cut the elastic (waist measurement + 1″ for overlap).
  6. Using a safety pin or bodkin, thread the elastic through the casing. Pin the ends and try on the pants. Adjust the elastic if necessary, then stitch the ends together using a zigzag stitch.
  7. Finish stitching the casing closed. You may need to stretch the waistband with both hands to make it smooth enough to sew.
  8. To keep the elastic from twisting inside the casing, “stitch in the ditch” through the casing at each vertical seam (center front, center back, side seams)

Finish with ribbing cuffs

    Finished sweatpants

    Finished sweatpants

  1. Stitch the ends of the cuff together to form a circle.
  2. Fold the cuff in half, right sides together.
  3. Divide the cuff in quarters and pin-mark each quarter.
  4. On the bottom edge of the pant leg, pin-mark halfway between side seam and inseam on both front and back.
  5. Pin the cuff to the pant leg right sides together (right side of pant leg facing the cuff) and distribute the fullness of the pant leg.
  6. Stitch or serge the cuff to the pant leg.

Voila! Now you have a great new pair of sweatpants.

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