Calculators · Spray Foam Insulation Calculator

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Spray Foam Insulation Calculator

Enter your area and thickness, or the R-value you want, to get the board feet of foam and the number of kits to buy.

Area 1

Shape

Length

Width

Openings to subtract (sq ft)

Optional. Windows, doors and anything you will not foam. Empty means 0.

Thickness (in)

The thickness of the cured foam, in inches.

Foam or kit

Choose a product to fill the two boxes below, or type your own values.

R-value per inch

From the data sheet of your foam.

Board feet per kit

Optional. The rating on the kit, at 1 inch thick. Leave it empty to get only the board feet.

Yield you expect (%)

Optional. The share of the kit rating you expect to get. Empty means 100%.

Extra to add (%)

Optional. For waste or uneven surfaces. Empty means 0.

How to calculate spray foam insulation

Spray foam is priced and rated in board feet. One board foot is one square foot of foam one inch thick. DAP defines it on its data sheet as a 12 in by 12 in square at 1 in thick. So the foam you need is the area times the thickness.

Step	Formula
1. Net area	length × width of each surface − windows and doors (triangle: base × height ÷ 2)
2. Thickness	the inches you type, or R-value you want ÷ R-value per inch
3. Board feet	net area × thickness × (1 + extra ÷ 100)
4. Kits	board feet ÷ (board feet per kit × yield ÷ 100), rounded up

The calculator reads measurements typed like 10'6" or 10 ft 6 in and accepts feet, inches, yards and meters. Add one area for each wall, roof section or gable end and the total updates as you type. The R-value you get is the thickness times the R-value per inch.

Example 1: a wall with a 600 board foot kit

A wall measures 20 ft by 10 ft and you want 2 inches of foam from a Touch 'n Foam kit rated at 600 board feet, with the R-value per inch from its data sheet.

Step	Operation	Result
Area	20 × 10	200 sq ft
Board feet	200 × 2	400 bf
R-value	2 × 6.4	R-12.8
Kits	400 ÷ 600 = 0.67, rounded up	1 kit

The kit rating is a theoretical figure. If you expect to get 70% of it, one kit gives 420 board feet, and 400 board feet still fits in one kit. Change the yield box to see where the count jumps to two kits.

Example 2: 1,000 sq ft at R-30

You want R-30 on 1,000 sq ft with DuPont FROTH-PAK 630 kits (R-12.2 at 2 inches, so 6.1 per inch, and 630 board feet). Choose that kit and the “I know the R-value” tab.

Step	Operation	Result
Thickness	30 ÷ 6.1	4.92 in
Board feet	1,000 × 4.918	4,918.03 bf
Kits of 630 bf	4,918.03 ÷ 630 = 7.81, rounded up	8 kits
Passes	4.918 ÷ 2 in per pass, rounded up	3 passes

DuPont says FROTH-PAK can be applied up to 2 inches thick in one pass, so a thickness of 4.92 inches means at least three passes. That limit comes from that product. Other foams have other limits.

Board feet for common areas

Area	1 in	2 in	3 in	4 in
100 sq ft	100	200	300	400
250 sq ft	250	500	750	1,000
500 sq ft	500	1,000	1,500	2,000
1,000 sq ft	1,000	2,000	3,000	4,000

Kit yields and R-values from the manufacturers

The kits below are the ones in the calculator. The board feet are the manufacturer's theoretical yield at 1 inch, from the DAP data sheet (January 2025) and the DuPont pages for the FROTH-PAK 200 and the FROTH-PAK 630. We read all three in October 2026. The calculator uses the 2 inch R-value divided by 2 as the R-value per inch.

Kit	Board feet (theoretical)	R at 1 in	R at 2 in	Sq ft at 1 in	Sq ft at 2 in	Sq ft at 3 in
DAP Touch 'n Foam 200	200	6.4	12.8	200	100	66.7
DAP Touch 'n Foam 600	600	6.4	12.8	600	300	200
DuPont FROTH-PAK 200	200	6.2	12.2	200	100	66.7
DuPont FROTH-PAK 630	630	6.2	12.2	630	315	210

Both manufacturers warn that the theoretical yield is worked out in laboratory conditions, without counting the loss of blowing agent or the differences in how the foam is applied. DAP adds that temperature affects adhesion and yield, and recommends applying at 60 to 90 °F with the chemical contents at 70 to 90 °F.

Open-cell and closed-cell foam

If you do not have a data sheet, the calculator offers typical values from a U.S. Department of Energy Building America guide (last updated in 2009, checked October 2026). It lists open-cell foam at about R-3.6 per inch and closed-cell foam at R-6.1 per inch in its table, and R-6 in its text. It says closed-cell foam is typically limited to layers of 2 to 3 inches per pass, while open-cell foam can usually be applied to full thickness in one pass, generally up to 10 inches. The guide is old and the values vary by product, so replace them with the numbers of the foam you buy.

Tips for ordering

Use the rating on your kit, not a generic number. Kits of the same size from different brands can differ.
Lower the yield box if you expect less than the laboratory figure, and watch the kit count change.
Measure irregular spaces as several rectangles and triangles and add them with “Add another area”.
For a target R-value, check the R-value per inch on the data sheet. It is the number that sets the thickness.

Frequently asked questions

How do I calculate how much spray foam insulation I need?

Multiply the area in square feet by the thickness in inches. The result is in board feet, because one board foot is one square foot at one inch thick. A 200 square foot wall at 2 inches is 200 × 2 = 400 board feet. Subtract windows and doors first. Then divide by the board feet of one kit, which the manufacturer rates at a 1 inch thickness.

What R-value is 2 inches of spray foam?

It depends on the foam. The DAP Touch 'n Foam kit data sheet lists R-12.8 at 2 inches and the DuPont FROTH-PAK pages list R-12.2. The DOE guide we checked gives a typical R-6.1 per inch for closed-cell foam, which is R-12.2 at 2 inches, and R-3.6 per inch for open-cell foam, which is R-7.2 at 2 inches. That guide dates from 2009, so use the figure on your product data sheet when you have it.

How many square feet does a kit or a drum of spray foam cover?

Divide the board feet by the thickness in inches. A kit rated at 600 board feet covers 600 square feet at 1 inch and 300 square feet at 2 inches, as a laboratory figure. This page has no verified rating for a 55 gallon drum, because the figure depends on the product and the manufacturer, so use the board feet printed on your drum or set.

Why does a kit give less foam than its label says?

The kit rating is a theoretical yield. DAP and DuPont both say it is calculated in laboratory conditions, without counting the loss of blowing agent or the variations in how the foam is applied. DAP adds that temperature and humidity change the real output. Type a lower yield percentage in the calculator if you expect less.

How much does it cost to spray foam 1,000 square feet?

Prices change by region, product and contractor, so this calculator does not show them. At 2 inches, 1,000 square feet is 2,000 board feet. Ask suppliers or installers for a quote per board foot or per square foot at the thickness you want.

What is the difference between open-cell and closed-cell spray foam?

The DOE guide we checked says closed-cell foam is denser and has about R-6 per inch, while open-cell foam is about R-3.6 per inch. Closed-cell foam is usually applied in layers of 2 to 3 inches per pass, and open-cell foam can usually go on to its full thickness in one pass. The guide dates from 2009.

Can I use this to size a whole-house job or check code?

No. It counts the foam for the area and thickness you type. It does not decide how much your building needs, and it does not check code requirements, ventilation or fire protection. Follow the product label and data sheet, and ask the installer or your local building department.

Buying batts, rolls or blown-in bags instead? Use the insulation calculator. Nothing you type leaves your browser.