Okay, so for this particular tutu, the waist size was 20, make it a few inches shorter because it will get stretched a bit as you're tying the knots. Sew the ends together securely. I went along all four sides of the overlap. This is the only sewing you'll be doing.
I used white and light pink. If you roll them out together, you can make sure they're all the same length.
I cut this one at 23 inches. You'll need to double your length, in my case I wanted 12 inches, just below the knee for Kari, so you double it, 22, then add an inch for the knot. 23
I used all 25 yards of each roll for this one.
Put your elastic on a jug (it helps make sure everything is uniform) Fold your tulle in half, stick the loop up under the elastic
Pull the tails through..
tighten, move to the next knot. Keep them tight, but not so tight that you make it huge.
This one is Kari's. It's all glittery and sparkly, she LOVES it. :D