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Spray Foam Insulation Cost Calculator
Your project
Prices are typical installed US prices per board foot (one board foot = 1 sq ft at 1 inch thick). Closed-cell runs about $1.00–$1.50 per board foot; open-cell about $0.40–$0.65. Your contractor’s quote is the final word — use this to check it, not replace it.
Example: 1,000 sq ft at 3 inches of closed-cell foam → 3,000 board feet at $1.00–$1.50 per board foot = $3,000–$4,500, about $3,750 in the middle, or $3.75 per sq ft.
Behind the numbers
How spray foam cost is calculated
Spray foam is priced by the board foot: one board foot covers 1 square foot at 1 inch thick. Multiply your area by the thickness in inches to get the board feet, then multiply by the price per board foot. Closed-cell foam costs more per board foot but gives about R-6.5 per inch, so 3 inches is about R-19.5; open-cell foam is cheaper at about R-3.6 per inch, so the same 3 inches is about R-10.8. The low and high ends of the range reflect real US installed prices, which vary by region, job size and how easy the area is to reach.
Worked example: 1,000 sq ft × 3 inches = 3,000 board feet. Closed-cell at $1.00–$1.50 per board foot: low 3,000 × $1.00 = $3,000, high 3,000 × $1.50 = $4,500, middle 3,000 × $1.25 = $3,750. R-value: 3 × 6.5 = R-19.5.
Reference
Spray foam prices and R-values
| Foam type | Price per board foot | R-value per inch | Best for |
|---|---|---|---|
| Open-cell | $0.40 – $0.65 | About R-3.6 | Interior walls, attics, sound dampening |
| Closed-cell | $1.00 – $1.50 | About R-6.5 | Exterior walls, roofs, crawl spaces, moisture control |
Prices are typical installed US prices and vary by region and job size. Open-cell foam is softer and lets water vapor through; closed-cell foam is rigid, resists moisture and adds stiffness to the structure.
Worked examples
Example spray foam jobs
| Job | Board feet | Cost range | Middle estimate | R-value |
|---|---|---|---|---|
| 1,000 sq ft, 3 in, closed-cell | 3,000 | $3,000 – $4,500 | $3,750 | R-19.5 |
| 1,000 sq ft, 3.5 in, open-cell | 3,500 | $1,400 – $2,275 | $1,838 | R-12.6 |
| 2,000 sq ft, 2 in, closed-cell | 4,000 | $4,000 – $6,000 | $5,000 | R-13 |
| 500 sq ft, 5 in, open-cell | 2,500 | $1,000 – $1,625 | $1,313 | R-18 |
Tips before you spray
Get at least two quotes and compare them per board foot, not just the total — the total hides differences in thickness and foam type.
Check the R-value your code requires before choosing thickness: 3 inches of closed-cell is about R-19.5, which is fine for many walls but short of the R-38 to R-49 most attics need.
Closed-cell costs roughly twice as much as open-cell, so use it where its moisture resistance pays off — roofs, crawl spaces and exterior walls — and open-cell where it does not.
Spray foam must be installed by a trained crew with proper ventilation and protective gear; this is not a DIY job, and a bad install is expensive to fix.
Good to know
Frequently asked questions
What is a board foot of spray foam?
One board foot is 1 square foot of coverage at 1 inch thick. Board feet = area in square feet × thickness in inches, so 1,000 sq ft at 3 inches is 3,000 board feet. Spray foam is priced per board foot because thicker jobs use more material.
How much does spray foam insulation cost?
Installed closed-cell foam runs about $1.00 to $1.50 per board foot and open-cell about $0.40 to $0.65. For 1,000 sq ft at 3 inches of closed-cell (3,000 board feet) that is $3,000 to $4,500, about $3,750 in the middle. Prices vary by region, job size and access.
Open-cell vs closed-cell — which should I choose?
Open-cell is cheaper and good for interior walls and sound dampening, at about R-3.6 per inch. Closed-cell costs more but gives about R-6.5 per inch, resists moisture and stiffens the structure, so it suits roofs, exterior walls and crawl spaces. Match the foam to the job, not just the price.
How thick should spray foam be?
It depends on the R-value your climate and building code require. Three inches of closed-cell foam is about R-19.5 and 3.5 inches of open-cell is about R-12.6, while most attics need R-38 to R-49. Divide your target R-value by the foam’s R-value per inch to find the thickness.