How do you figure square yards for carpet that will be installed on walls?

Just take the square footage and divide it by nine(9). For example; if your living room is 12x12 and your den is 15x21 then you would multiply 12x12=144, then multiply 15x21=315, add the two 144+315=459, then divide by 9, 459/9=51 total sq yrds. In order to get the square yardage for a role of carpet(12ft WIDE) all you have to do is take the length and multiply it by 1.33 and you will get the sq yrds. For ex. if you have a role 12x 223ft you just multiply 223x1.33=296.59yrds.