For our 13' Boler
I came up with 252 square feet or 28 square yards to completely cover the inside from floor to ceiling all the way around, if you don't put it below the dinette seats or inside the cabinets, etc. and after figuring in for the windows
& door we bought about 18 square yards. We haven't installed it yet but will within the next week or so, we went with a marine grade headliner from Hancock Fabrics at a really good price using their coupons and a sale on the fabric thanks to my wonderful coupon queen wife.