Spray Foam Insulation Calculator
Spray foam comes as two-component DIY kits (measured in board feet at 1" thick) and contractor-applied systems. Enter your area and desired R-value to get kit count, total board feet, and estimated material cost.
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Top PickClosed-Cell Spray Foam Kit 200 BF — Amazon~$149* Affiliate links — we may earn a commission at no cost to you.
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How to Use This Calculator
- 1Enter your measurements in the fields above. Use the units shown next to each field (ft, in, etc.).
- 2Click Calculate to get your material estimate instantly.
- 3Review the highlighted result — it shows the key quantity you need to order.
- 4Use Copy Results to save your estimate, or bookmark the URL — your inputs are encoded in the link.
Pro tip: Always add 10% to your material order to account for waste, cuts, and defects.
Frequently Asked Questions
How many board feet of spray foam do I need for a 200 sq ft crawl space?
For closed-cell foam at R-20 in a crawl space: R-20 / 6.5 R/inch = 3.1 inches thick. Board feet = 200 sq ft × 3.1 in = 620 BF. Use one 600-BF kit plus one 200-BF kit, or one 1500-BF kit if you have more areas to do.
What is the difference between open-cell and closed-cell spray foam?
Closed-cell foam (R-6.5/in) is dense, rigid, and acts as a vapor barrier — best for exterior walls, rim joists, and below-grade applications. Open-cell foam (R-3.7/in) is soft and spongy — better for interior walls and soundproofing where vapor barriers are not needed. Closed-cell costs about 2× more per board foot.