Measuring your Princess:
You’ll want to measure wrist to wrist or fingertip to fingertip. It just depends on how long you’d like it on the arms. You’ll also want to measure shoulder to ankle/floor. Again, it depends on how long you’d like it.
My daughter was about 20×20 when I measured her. I got a yard of fabric, which was 36 inches (a yard) and most fabric will measure 40 inches wide. So, one yard was plenty, and I’ll have left over. If your child measured about 40×40, you’d want to get 2 yards. We’ll be folding it in half, so you’ll need to double the length to make sure you get enough yardage.
To make things more simple, I just have my daughter lay down on the fabric. The fabric is folded in half (to measure 36×18). The fold is at the top, and I have her line her shoulders up with the folded edge.
As she laid down, I used my fabric scissors, and cut the shape I wanted the cape to be. I started towards the bottom edge and moved inward as I got closer to her arms.