1) Select an old pair of pants or jeans that fit you well (or find a well-fitting pair at a thrift store or store sale). Take photographs of the pants front and back, and details of the different seam parts such as the zipper attaching seam, pockets, belt loops, hem, or any special sewing details you will need to duplicate for reference.
2) Using a seam ripper, cut each seam—pockets, belt loops, waistband and zipper—making sure to cut only through the thread and not the fabric.
3) Remove the loose thread from all the pieces, then iron them flat. The marks from the old seams will still be visible to indicate the seam allowances you will need to maintain for the new pants.
4) Pin each piece of the pants to a sheet of paper that’s larger than the piece of fabric.
5) Trace the outline of each piece of pants on the paper with a pencil or pen, noting all the important markings such as placement of the pockets or location of belt loops on the waistband.
6) Remove the pieces of fabric from the paper. Make sure to take the time to label each piece of paper with the name of your pants project as well as the name of each part of the pants. For example, ‘grey pants’ and ‘front leg’.
7) Pre-wash and dry your store-bought or re-used fabric according to the instructions for the fabric or the same way you plan to wash your finished pants, then iron the fabric flat.
8) Place the fabric pattern side up on a large flat surface such as a desk, making sure to use the correct side of the fabric if the fabric has two sides or prints.
9) Pin each piece of the paper pattern on top of the flat fabric and mark the outline of the pattern onto the fabric using a fabric marker. The fabric marker will come off the fabric in the first wash, or you can rub it out of the fabric with an eraser. Make sure to mark any special features on the fabric such as pocket or belt loop locations.
10) Remove the paper pattern and cut each piece of the pattern out of the fabric. The original seam allowances will be built into your pattern.
11) Pin all the cut fabric pieces together, right sides facing each other, starting with the front and back of the legs in the same way the original pants were sewn. Refer to your photographs if you can’t remember details.
12) Sew all parts together on the back (or wrong) side of the fabric, keeping the same amount of seam allowance as in the original pants. Start by sewing the legs together. Next, sew the zipper and then the waistband, followed by any smaller details such as pockets or belt loops. Use a regular straight stitch for all the main seams and a zigzag stitch for finishing off the edges of the seam allowance to prevent the fabric from unraveling.
13) Last, try the pants on with the same type of shoes you plan on wearing with the pants. Have a friend help you pin the hem at the desired length, or you can do this yourself by trial-and-error, trying on the pants several times until you are happy with the pants length. Sew the final hems.
14) Your pants are ready to go!