Tulle

Figure approx. 1 yard from back of row to back of next row, allow extra to swag x 4 rows x 2 aisles plus a little extra to hang down on the first and last rows -- maybe 15-20 yards? Better to have a little too much than too little.

Ok Im doing the same thing and my event coordinator told me the exact Im going to see if I can find the email and tell you

I would figure about 1 1/2 to 2 yards per swag. Tulle comes in really wide width (58-60") so depending on how thick you want the swags to be you could probably cut the tulle in half down the lenghth of the bolt. So technically you would need 7 1/2-10 yards to do both sides of the aisle, but since tulle is so inexpensive I'd buy a few more yards just to be safe. If you have a Joanns or Hobby Lobby by you, use a coupon and get it really cheap.

Michael's also sells bolts of tulle and distributes lots of coupons.

Ok heres what she said: for 6-7 rows of chairs you need to swag it so that would be about 6yrds plus maybe 1 extra yard so it's not just straight. I've attached a picture of what I'm doing mine will be outside like your picture as well.