Calculator 11 / Insulation
Insulation Calculator
Figure bags/rolls needed for batt insulation, or board feet and kits needed for spray foam.
How this calculator works
A "board foot" of spray foam is 1 square foot covered at 1 inch of thickness — the standard unit the industry sells foam kits by. Batt/roll coverage is left as a field you fill in from the product label rather than a hardcoded assumption, since coverage per bag varies by R-value, batt width, and manufacturer.
Open-cell vs. closed-cell — does it change the math?
Not the board-foot math itself — that's pure area × thickness. The foam type matters for how much R-value you get per inch (closed-cell roughly doubles open-cell's R-value per inch), which affects what thickness you should target in the first place.
Why is waste higher for spray foam than batts?
Spray foam overspray, trimming proud foam flush with framing, and uneven cavity fill typically account for more material loss than cutting batts to fit — 15% is a reasonable starting point versus 10% for batts.
Estimates only. Confirm exact coverage and yield figures against your specific product's data sheet, and consult a licensed insulation contractor for code-required R-values in your climate zone.