Spray-Foam Board-Feet & Set Calculator
Board-feet = area × thickness. Divide by the kit yield to get how many sets or DIY kits to buy.
Calculator
500 ft² at 2.0" is 1,000 board-feet — about 2 kit(s) at 600 bd-ft each. 1 board-foot = 1 ft² at 1 inch; kit/set yields are labeled — confirm on the kit; real yield drops with temperature and waste.
Spray foam is bought in board-feet — one board-foot is one square foot sprayed one inch thick. Nail that unit and everything else follows: multiply your area by the depth, divide by what a kit yields, round up. This tool does it and warns you that the printed yield is a best case.
The default sizes 500 ft² sprayed 2″ deep in closed-cell, against a 600 bd-ft DIY kit.
Formula
board_feet = area_sqft × thickness_in
sets = ceil( board_feet ÷ yield_per_set )
1 board-foot = 1 ft² at 1″. A 600 bd-ft kit theoretically covers 600 ft² at 1″, or 300 ft² at 2″, and so on.
Worked example
500 ft² at 2″ closed-cell. Board-feet = 500 × 2 = 1,000 bd-ft. Against a 600 bd-ft kit: 1,000 ÷ 600 = 1.67 → 2 kits. You will finish with foam to spare — plan an offcut area to use it before it kicks.
Background & practice
Nominal yield is optimistic. The board-foot rating on a kit assumes ideal chemical temperature, a steady trigger and minimal waste. Cold tanks, a stop-start pattern and off-ratio passes all cut real yield — budget 10–20% short of the label on DIY kits, and always round up a set.
Open vs closed changes the depth, not this math. Open-cell (~3.5/in) needs almost twice the depth of closed-cell (~6.5/in) for the same R, so it burns more board-feet for the same R-value. Pick the depth for your target R first, then run the board-feet.
What to measure first: the true area (rafter bays, gable walls, rim joists), the depth you can legally leave exposed vs the thermal/ignition barrier the code wants, and the tank temperature. For the R-value side of open vs closed, use the compare tool.
Reference table
| Area × depth | Board-feet | Small kits (200 bd-ft) | Large kits (600 bd-ft) |
|---|---|---|---|
| 200 ft² × 1″ | 200 bd-ft | 1 | 1 |
| 200 ft² × 2″ | 400 bd-ft | 2 | 1 |
| 200 ft² × 3″ | 600 bd-ft | 3 | 1 |
| 500 ft² × 1″ | 500 bd-ft | 3 | 1 |
| 500 ft² × 2″ | 1,000 bd-ft | 5 | 2 |
| 500 ft² × 3″ | 1,500 bd-ft | 8 | 3 |
| 1,000 ft² × 1″ | 1,000 bd-ft | 5 | 2 |
| 1,000 ft² × 2″ | 2,000 bd-ft | 10 | 4 |
| 1,000 ft² × 3″ | 3,000 bd-ft | 15 | 5 |
Labeled DIY kit yields; pro rigs vary. Real yield runs ~10–20% under the label — round up and keep a spare cartridge.