If you want to make your own sweat pants, you do not need to buy a pattern. You can simply use your favourite old pair of sweat pants. Always wash and dry fabrics before you cut and sew the material, according to Simplicity.
Lay fabric flat on the worktable. Fold the material in half to cut two pieces of fabric. The fabric should have the right sides facing each other. For example, the inside of the finished sweat pants will be the fuzzy side of the material. The smooth side of the fabric refers to the right side of the trousers. The right side shows on the outside of the finished product.
Turn the trousers you chose for your pattern inside out. Turn the material with the seam showing on the outside.
Fold trousers with the front sides together as if you are going to hang them on a hanger. Make sure the crotch area is showing. This is the back of the new trousers.
Place the trousers on the fabric close to the edge of the folded material. Smooth out all the wrinkles and make sure the legs and waist are even with each other.
Pin the trousers to the fabric. Cut the fabric about half an inch wider along the sides and crotch of the trousers to the waistline. Cut the material 2 1/2-inches longer when you cut along the waist of the trousers-pattern and allow 1- to 1-1/2 inches for the hem of the new sweat pants.
Mark the fabric with a pencil labelled "b" for back. Remove the pins from the trousers, and refold the trousers with the backsides together. This is the front of the new trousers. The front crotch area is a little shorter than the back crotch area.
Secure the trousers to the fabric with pins, and cut around the pant pattern as you did in Step 5. Allow for the same measurements. Mark the fabric with a pencil labelled "f" for the front of the new trousers before removing the pins.
Align the "b" pieces of cut fabric at the waist and crotch with the right sides of the material facing each other so the seam will show on the fuzzy inside of the material.
Begin sewing at the waist and sew through the end of the crotch area. The seam width should be the width of the seam on your old trousers. Repeat the process in Steps 1 and 2 for the two pieces marked "f."
Line up the sides of the front and back panels you created in Steps 1 and 2 with the seam showing on the outside. Sew the sides together from the waist through the end of the raw hem edge.
Sew the inside seams together starting at the bottom of one leg through the crotch and down the second inside seam through the end of the raw hem edge. Adjust the material as necessary. The crotch seams should match as much as possible.
Fold the waist about 2-1/2 inches. Turn the edge under about 1/2 inch and hem. Begin at one side of the centre seam of the pant's front and sew the entire waist back to the centre. Stop sewing at the opposite side of the centre seam from where you started. Leave an opening large enough to thread a drawstring through the waist. Back stitch or tack the opening on either side to keep the thread from pulling loose.
Turn the leg hem edges under about half an inch. Pull material from above back over the turned edge, about a quarter of an inch, and blind stitch the hem shut, according to suggestions by Craftstylish.
Place pins in a bowl or use a pin cushion to keep track of them.