Spray Foam Insulation Calculator

How to estimate spray foam

Board feet = sq ft × thickness in inches. Divide by the kit yield for kit count. Add 10–15% — cold temperatures and fast technique reduce actual yield. Closed-cell requires multiple thin passes; never exceed 2 inches per pass.

Spray foam FAQ

How do I calculate spray foam insulation?

Spray foam is measured in board feet (bf). One board foot covers 1 square foot at 1 inch thick. Multiply your area by the target thickness in inches to get total board feet, then divide by the kit size (typically 200 bf for closed-cell, 600 bf for open-cell kits).

What is the R-value of spray foam?

Closed-cell spray foam provides about R-6.5 per inch, making it the highest R-value per inch of any common insulation. Open-cell foam runs about R-3.8 per inch but is less expensive and great for sound dampening.

Closed-cell vs open-cell spray foam: which do I need?

Use closed-cell for exterior walls, crawl spaces, and anywhere you need a vapor barrier, high R-value in a thin space, or structural rigidity. Use open-cell for interior walls, attic decks, and sound control where moisture is not a concern.

How many cans of spray foam do I need?

Small cans (like Great Stuff) are for gap-filling and seal roughly 12–15 board feet per can. For insulating large areas, use 2-component contractor kits — small kits yield about 200 board feet, larger ones 600+ board feet.