Spray foam calculator: how much spray foam do I need?
1 kit
160 board feet · 80 sq ft at 2 in · R-13.4 at 6.7 per inch · for 10 × 8 ft, Froth-Pak 210 kits
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3/8 or 10' 6".
1 kit
160 board feet · 80 sq ft at 2 in · R-13.4 at 6.7 per inch
Source: DuPont Froth-Pak Insulation Spray Foam, Product Information Sheet 43-D100067-enUS-0521, read October 19, 2026. Data sheet (PDF)
An 8 by 10 ft wall sprayed 2 inches thick is 160 board feet of foam, so 1 kit of Froth-Pak 210, which its data sheet rates at 210 board feet, for about R-13.4 at 6.7 per inch.
A worked example
A crawl space wall 23.5 ft long and 7.75 ft high, sprayed 1.5 inches thick with Froth-Pak 210 kits needs 2 kits of Froth-Pak 210. The wall is 182.1 square feet; at 1.5 inches that is 273.2 board feet, and 273.2 ÷ 210 is 1.3 kits, so 2. At 6.7 per inch the layer is about R-10.
What is a board foot of spray foam?
One square foot of foam one inch thick. Kits are sold by board feet, so a kit's number is how many square feet it covers at 1 inch: a Froth-Pak 210 covers 210 square feet at 1 inch, 105 at 2 inches and 70 at 3 inches, in theory. 100 square feet at 3 inches is 300 board feet, 2 kits of 210.
What is the R-value of spray foam per inch?
For Froth-Pak closed-cell foam, R-6.7 per inch when new, the minimum in its data sheet. Aged 180 days at 75°F, a 1 inch layer tests at R-6.2 and a 2 inch layer at R-12.2. To hit a target R, divide it by 6.7: R-13 is about 2 inches.
What else it is called
A spray foam calculator is also searched as a spray foam insulation calculator or a board foot calculator for spray foam. Open-cell foam and other brands of kit print their own yield and R-value; the figures here are Froth-Pak's closed-cell kits.
Board feet and kits by area
| Area | Board feet at 1 in | Board feet at 2 in | Froth-Pak 210 kits at 2 in | Froth-Pak 650 kits at 2 in | R at 2 in |
|---|---|---|---|---|---|
| 25 sq ft | 25 | 50 | 1 | 1 | R-13.4 |
| 50 sq ft | 50 | 100 | 1 | 1 | R-13.4 |
| 100 sq ft | 100 | 200 | 1 | 1 | R-13.4 |
| 150 sq ft | 150 | 300 | 2 | 1 | R-13.4 |
| 200 sq ft | 200 | 400 | 2 | 1 | R-13.4 |
| 300 sq ft | 300 | 600 | 3 | 1 | R-13.4 |
| 500 sq ft | 500 | 1000 | 5 | 2 | R-13.4 |
Kits at the theoretical yield in Froth-Pak's data sheet (210 and 650 board feet, calculated at 1 in thick in laboratory conditions; the sheet says real yield is lower). R at the initial 6.7 per inch; aged 180 days, the sheet gives R-12.2 for a 2 in layer.
Where the numbers come from
- Kit yields and R-value: DuPont's Product Information Sheet for Froth-Pak Insulation Spray Foam (43-D100067-enUS-0521). Table 1 gives the Froth-Pak 210 kit 210 board feet and the Froth-Pak 650 kit 650, «calculated at 1” thick» in laboratory conditions, and says real yield is lower; Table 2 gives an initial R-value of 6.7 per inch (ASTM C518, minimum), and after 180 days R-6.2 for a 1 inch layer and R-12.2 for 2 inches. Read October 19, 2026. Data sheet (PDF)
- A board foot is one square foot one inch thick, the unit of the data sheet's yields, so board feet = square feet × inches of foam; kits are rounded up.
The kit yields are theoretical: DuPont measures them in laboratory conditions and says that blowing agent loss and the way the foam is sprayed make the real yield lower, without giving a figure, so a job that lands close to a kit's yield runs out before it.
By Javier Miralles · Last updated . How this site is made.
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