Here is a simple calculator to know how much roll insulation you need for your home improvement project. It is actually very simple to calculate this, you don’t even need to have a calculator. However, here it is for your convenience;
The number of roll insulations you need to buy solely depends on the square feet area of the place you want to insulate. For that, you need to input the height and width or length and width of the area into the calculator above. This will give you how many square feet that area is, and that is how much roll insulation you need.
As you know, roll insulation comes in rolls. These rolls already have a fixed thickness, area and R-value rating. Therefore, once you decide on the R-value, all you need to do is buy enough square feet of the insulation with that R-value rating.