Spray Foam Insulation Cost Calculator (Metric)
Enter your wall area, foam depth, and price per board foot to estimate the board feet and total cost.
What your result means
Spray foam is priced by the board foot, which is 0.1 m² at 2.5 cm deep, so board feet is your area times the depth. Open-cell runs $0.50 to $1.50 a board foot at about R-3.5 an inch; closed-cell is $1.50 to $3.50 at R-6.5 an inch and doubles as a vapor barrier. Add 10% for over-spray, and leave the install to a pro since it off-gases while curing.
How to use this calculator
- Calculate wall sq ft.
- Pick depth (open-cell typically 3-12.7 cm, closed-cell 5.1 cm).
- Get quote per board foot.
- Read board feet and total cost.
- Add 10% for over-spray waste.
The formula
Board feet is the wall area times the depth in inches. Multiply by your price per board foot for the total.
Worked example
Say you're foaming 46.5 m² of wall 7.6 cm deep at $1.50 a board foot. That's 1,500 board feet, or $2,250.
Spray foam by type
| Type | Price / board ft | R-value |
|---|---|---|
| Open-cell | $0.50 – $1.50 | R-3.5/in |
| Closed-cell | $1.50 – $3.50 | R-6.5/in |
Tips & gotchas
- A board foot is 0.1 m² at 2.5 cm deep.
- Open-cell foam is cheaper with a lower R-value (R-3.5 an inch).
- Closed-cell costs more but hits R-6.5 an inch and acts as a vapor barrier.
- Foam expands, so measure the depth after it cures.
- Use a pro for the install; it off-gases while curing.
Frequently asked questions
How much does spray foam cost?
$1 to $3 a board foot. A whole house runs $5,000 to $15,000.
Is spray foam worth it?
For air sealing and a high R-value, yes. It often pays back in 5 to 10 years on energy.
Open-cell or closed-cell?
Open is cheaper at R-3.5 an inch; closed is $1.50-plus a board foot at R-6.5 with a vapor barrier.
Can I install spray foam myself?
DIY kits work for small areas; a whole house needs pro equipment.
Is spray foam safe?
Yes once cured. It off-gases during install, so wear PPE and stay out 24 hours.
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Estimates only — see our full disclaimer.