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Spray Foam Calculator

Enter the area and thickness to size your spray foam order.

Result

1,600.00 bd-ft
3
600 bd-ft

How it is calculated

A board foot is 1 square foot of foam at 1 inch thick, so the tool calculates board feet = area × thickness and kits = ⌈board feet ÷ board feet per kit⌉. Area is in square feet, thickness in inches and kit yield in board feet. If the kit field is empty or zero, the tool assumes a 600 board-foot kit, so check the yield printed on your product, as kits differ. The kit count is always rounded up to a whole kit. There is no waste or overspray allowance and no adjustment for cold weather, so add your own margin. Area and thickness must be above zero. The tool does not tell you which foam type or R-value you need.

Worked example

You want to spray 800 square feet of roof deck with 2 inches of foam, using kits rated at 600 board feet. Step 1: 800 × 2 = 1,600.00 bd-ft. Step 2: 1,600 ÷ 600 = 2.67 kits. Step 3: round up to 3 kits. With 3 kits you have 1,800 bd-ft, which leaves about 200 bd-ft spare. If your kits were rated at only 200 bd-ft, the same job would take 8 kits.

Try this example →

Common mistakes

  • Leaving the kit size at the default when your product has a different yield. The default is 600 bd-ft, but a 200 bd-ft kit means 8 kits for the same job instead of 3.
  • Entering thickness in millimetres or centimetres. The field is in inches, so 2 inches is 2, not 50.
  • Entering area in square metres. The tool expects square feet, and 1 square metre is about 10.76 square feet.
  • Ignoring the actual number of passes. A 4-inch layer is usually sprayed in several thinner lifts, but the board-foot total is the same, so the tool does not change with passes.
  • Treating the rounded-up kit count as including waste. It only rounds to whole kits, so in the example the 3 kits leave only 200 bd-ft spare on a 1,600 bd-ft job, and 13% waste or more would need a fourth kit.

About this calculator

Spray polyurethane foam is measured in board feet — one board foot covers 1 square foot at 1 inch of thickness — so the total board feet needed is simply the area in square feet multiplied by the target thickness in inches. Open-cell and closed-cell foam kits are sold with a rated board-foot yield (check the label; common kit sizes run from a few hundred to about 600 bf or more), which determines how many kits a job requires.

This calculator takes the area to be sprayed and the desired thickness, converts it to total board feet, and divides by a kit's rated yield to tell you how many kits to buy, rounding up to the next whole kit. If you leave the kit yield blank it assumes 600 board feet per kit. It adds no extra allowance, so if you expect yield to drop in cold weather or with an inexperienced sprayer, add a margin to the area or thickness. Insulation contractors and DIY homeowners use it when quoting or budgeting a rim-joist, attic, or crawlspace insulation job before ordering foam.

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Comments (1)

  • Editorial team

    The kit yield is the number that moves this result most, and it differs between products and between foam types, so enter the board-feet figure printed on your kit instead of leaving the default. The tool rounds up to whole kits and adds no allowance for overspray or uneven surfaces. For the 800 sq ft job at 2 inches it gives 3 kits with about 200 bd-ft spare. What yield does your kit state?

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