How Many Board Feet of Spray Foam Do I Need? Kits Chart
Spray foam is sold in board feet: one square foot sprayed one inch thick. A wall 40 ft long and 8 ft high sprayed 3 in thick needs 960 board feet, and with 10% extra that is 2 kits of 600 board feet. The spray foam insulation calculator does it for your area.
Part of the project planner: Planning a roof replacement.
Board feet and kits for common areas
3 in thick, with 10% extra.
| Area | Board feet | Kits of 200 | Kits of 600 |
|---|---|---|---|
| 100 sq ft | 300 | 2 | 1 |
| 200 sq ft | 600 | 4 | 2 |
| 320 sq ft | 960 | 6 | 2 |
| 500 sq ft | 1,500 | 9 | 3 |
| 800 sq ft | 2,400 | 14 | 5 |
| 1200 sq ft | 3,600 | 20 | 7 |
How the thickness changes it
For a wall of 40 × 8 ft, with 10% extra, in kits of 600 board feet:
| Thickness | Board feet | Kits | One kit covers |
|---|---|---|---|
| 1 in | 320 | 1 | 600 sq ft |
| 2 in | 640 | 2 | 300 sq ft |
| 3 in | 960 | 2 | 200 sq ft |
| 4 in | 1,280 | 3 | 150 sq ft |
| 5 in | 1,600 | 3 | 120 sq ft |
| 6 in | 1,920 | 4 | 100 sq ft |
Choosing the thickness
- Take the R-value per inch from the data sheet of your foam: open cell and closed cell are different.
- Divide the R-value you want by the R-value per inch to get the thickness.
- Spray in the passes the maker allows. A thick pass can overheat.
Before you spray
- Read the kit label for the board feet it gives, the temperature range and the cure time.
- Wear a respirator, eye protection and coveralls, and ventilate the space as the maker says.
- Check the local code for the thickness and for any cover over the foam.
See also the attic insulation calculator and the weatherstripping calculator. The yield of a kit varies, so buy a little extra.
Frequently asked questions
How do I calculate board feet of spray foam?
Multiply the area in square feet by the thickness in inches. 320 sq ft at 3 in is 960 board feet.
What is a board foot of spray foam?
One square foot sprayed one inch thick. It is not the same as a board foot of lumber.
How many kits do I need?
2 kits of 600 board feet for 960 board feet with 10% extra.
How much does one kit cover?
A 600 board foot kit covers 200 sq ft at 3 in, and a 200 board foot kit a third of that.
How much waste should I allow?
10 to 15%, because foam is lost on rough surfaces, edges and overspray, and the yield varies.
More guides
Tools & materials for this project
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and follow local building codes for anything structural.