Measure your Jedi: You’ll want to measure wrist to wrist (or hand to hand, depending on how long you want the sleeves), then shoulder to ankle.
Figure out how much fabric you need:For my son we measured about 37×37. So I double the length and rounded up to 80 inches. Fabric is usually about 40 inches wide, which was just right, but then I needed 80 inches tall (since you’ll need a front and back for the robe, you’ll need the length x2). 36 inches is a yard so I needed about 2 1/4 yard.