Spray foam insulation cost calculator
Work out what spray foam should cost before you take a quote. Enter the surface area, pick open or closed cell, and give a target R-value; the calculator converts that to depth, then to board feet, then to an installed price range from dated national sources.
How the estimate is worked out
- Depth from R-value. Inches = target R ÷ R per inch. Open-cell is R-3.6 per inch. Closed-cell is R-6.8 to R-7.1 per inch, so a closed-cell estimate spans two depths.
- Board feet. Board feet = square feet × inches. Spray foam is priced by board foot, which is why depth matters as much as area.
- Installed cost. Open-cell $0.60 to $1.60 per board foot. Closed-cell $1.30 to $3.10. The thinner depth pairs with the lower rate and the thicker depth with the higher one.
- Rounding. Dollars are rounded to the nearest $100, because a national range cannot justify more precision than that.
What this calculator deliberately leaves out
No local or city rate, because none of the published sources gives one. No labour split, removal, ignition or thermal barrier, mould work, or rebate dollar amounts. No typical depth for attic floors, crawl spaces or rim joists, because no source publishes one. Where we have no data, the calculator asks you instead of guessing.
Which foam to pick is a separate question from what it costs — see open-cell vs closed-cell.
Which area are you insulating?
Measure the surface being sprayed, not the floor area of the room. A vaulted roof deck can be half again the footprint beneath it, and that difference is the single biggest reason an estimate comes in wrong.
| Area | Typical depth |
|---|---|
| Attic floor | No published typical depth, so enter a target R-value or a depth |
| Roof deck (underside) | 6 in open-cell, 3 in closed-cell |
| Walls | 3.5 in open-cell, 2 in closed-cell |
| Crawl space walls | No published typical depth, so enter a target R-value or a depth |
| Rim joist | No published typical depth, so enter a target R-value or a depth |
Where the table says no published depth, the calculator requires you to enter one. We would rather ask than invent a number.
| Target | Open-cell depth | Open-cell cost | Closed-cell depth | Closed-cell cost |
|---|---|---|---|---|
| R-13 | 3.61 in | $2,200 to $5,800 | 1.83 to 1.91 in | $2,400 to $5,900 |
| R-21 | 5.83 in | $3,500 to $9,300 | 2.96 to 3.09 in | $3,800 to $9,600 |
| R-30 | 8.33 in | $5,000 to $13,300 | 4.23 to 4.41 in | $5,500 to $13,700 |
| R-38 | 10.56 in | $6,300 to $16,900 | 5.35 to 5.59 in | $7,000 to $17,300 |
| R-49 | 13.61 in | $8,200 to $21,800 | 6.9 to 7.21 in | $9,000 to $22,300 |
Worked examples
Each line below is produced by the same code the calculator above runs, so the numbers on this page cannot drift from the numbers it gives you.
1,000 sq ft attic floor, target R-38, open-cell
38 ÷ 3.6 R per inch = 10.56 in deep. 1,000 sq ft × 10.56 in = 10,556 board feet. At $0.60 to $1.60 per board foot installed: $6,300 to $16,900.
The same attic in closed-cell
Closed-cell reaches R-38 in less depth, so the range spans two depths: 38 ÷ 7.1 = 5.35 in (5,352 board feet) up to 38 ÷ 6.8 = 5.59 in (5,588 board feet). At $1.30 to $3.10 per board foot installed: $7,000 to $17,300.
A small job: 150 sq ft rim joist, 2 in closed-cell
150 sq ft × 2 in = 300 board feet, which works out at $400 to $900. A job this small is where minimum fees decide the bill: many companies charge minimum job fees of $1,000 to $2,000 or more (HomeGuide, Dec 1, 2025). The calculator shows that note on any estimate under $2,000 and never adds it to the price, because we cannot know whose minimum applies to you.
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Already have a quote?
This page answers "what should this cost?". If you are holding a bid and want to know whether it is fair, use the spray foam quote checker instead — it works back from the price you were given.