Step 1: Take an old sweater, cut off the 2 sleeves, and cut off the bottom of the sweater (which you will use for the top of the leggings) .
The bottom of your legging will already be finished off and will require no sewing. The top of the arm (part of the sleeve that was closest to the shoulder) will need to be finished off.
Step 2: Measure the widest part of your calf. You will need to cut the bottom of your sweater into 2 pieces that size.
Step 3: Pin the unfinished side of the sweater bottom to the top of the sleeve to sew together
I hate using a sewing machine, so I hand-stiched them together and did a simple running sitch right under my first set of stitches to make sure it did not unravel. I’m sure using a sewing machine would have been MUCH easier and look nicer overall, but again I hate my sewing machine and this worked just fine.
(The black ribbon was a DIY fix because the top of the leggings were too big)
And the rest of the sweater?