Insulation Calculator
Turn wall, ceiling or floor areas into whole insulation packages using the coverage printed on your product.
How it works
Use the package label as the source of truth
Insulation package coverage varies by product thickness, R-value, cavity width and batt or roll dimensions. DIYSum therefore uses the coverage value you enter rather than assuming a universal package size.
Does this choose the correct R-value?
No. Required R-values and assemblies depend on climate, location in the building and applicable energy code. Confirm those requirements separately.
Should I subtract windows and doors?
You can subtract openings, but keeping a modest extra allowance can help cover trimming and irregular cavities.
Real-world project example
How many insulation rolls for a 20 × 30 ft attic?
A simple 20 × 30 ft rectangular ceiling area measures 600 sq ft. With 10% extra, that is 660 sq ft of nominal coverage. If a package covers 50 sq ft at the required thickness, 660 ÷ 50 = 13.2, or 14 packages rounded up.
Before you buy materials
Use package coverage at the selected R-value and thickness; rolls and batts may cover different areas. Avoid blocking soffit ventilation, and check local energy-code and fire-safety requirements.
Adjust the measurements, waste allowance and purchase options in the calculator above to estimate your own project; examples are for planning only.