01What this calculator estimates
Spray foam insulation is priced by the square foot of surface area to be covered, multiplied by the thickness in inches to get the board feet of foam. This spray foam insulation cost calculator works out the board feet required for your project and then provides a realistic installed cost for either open-cell or closed-cell spray foam insulation. The R-value you will get from the foam is also provided.
Many of the free online calculators that are listed use a simple flat rate based on square footage. The problem with that method is that it does not account for thickness. This home improvement tool calculator uses the board-foot method which allows for accurate calculations whether it is for a 2 inch thick insulation in a wall cavity or for 6 inch thick insulation in an open-cell attic. Related home improvement tools include an electrical load calculator and a tankless water heater sizing calculator.
02Open cell vs closed cell: cost and performance
When selecting the correct type of foam to use for insulation, thickness is a key consideration however choosing the correct type of foam is just as important. As mentioned in the ENERGY STAR Seal and Insulate guide, spray foam is one of the most effective materials for both air-sealing and insulating however there are two forms of spray foam; each serving a separate purpose at vastly different price points.
03Factors that change the final installed cost
The board-foot estimate here is a solid starting point, but several real-world variables shift the final contractor quote up or down:
- Labour rates by region. Contractor costs vary widely — a Midwest quote may be 20–30% below a coastal metro for the same spec. The EPA’s spray polyurethane foam guidance recommends using licensed applicators regardless of price.
- Surface prep and masking. If framing, wiring or HVAC ducts need masking before spray, add $0.10–$0.25/sf in labour.
- Accessibility. Low crawlspaces, attic kneewall areas or multi-storey scaffolding work increase setup time and cost.
- Existing insulation removal. If old batt insulation must be removed first, budget $0.50–$1.50/sf extra.
- Climate-zone R-value targets. DOE IECC 2021 specifies R-38 to R-60 for attics depending on climate zone (see DOE climate zone map), which may require more thickness than you initially plan.
- Enter the total area in square feet (length × width for a flat surface; add all surfaces together for a full room or structure).
- Select the target thickness in the drop-down.
- Choose Open Cell or Closed Cell with the toggle.
- Press Calculate to see board feet, cost range and R-value achieved.
- Switch the foam-type toggle to compare both options instantly.
Planning other parts of a renovation? Our wall stud calculator and board and batten calculator cover framing and exterior cladding quantities.
Rates listed are average national installed prices for professional application. Bid prices will vary based on local labor, job site conditions, preparation and material cost at time of installation. DIY kits are approximately 30-50% less than tool listed and cover smaller area.
- Removal of existing insulation
- Required fire-code thermal or ignition barriers over foam
- Multiple lifts needed for thick closed-cell applications (max ~2 in per pass)
- Ventilation requirements for the space during and after installation
01The spray foam cost formula
The prices for spray foam insulation are listed based on board feet, where 1 board foot is 1 square foot of surface area multiplied by a thickness of 1 inch. To obtain the cost in dollars for a specific amount of spray foam insulation, multiply the number of board feet needed by the installed price per board foot. The R-value (insulation rating) for spray foam will be based on the type of spray foam and the thickness for which it was designed to be installed.
Where:
- area= total surface area to be sprayed in square feet.
- thickness= the desired spray depth in inches.
- low / high rate= the installed price range per board foot for the chosen foam type.
- R-value per inch= thermal resistance per inch of thickness (open-cell ~3.7, closed-cell ~6.5).
02Worked example
A homeowner wants to insulate a 1,200 sq ft attic deck with 4 inches of open-cell spray foam. Here is how the estimate works:
This option has an estimated installed cost of $2,112-$3,120 for R-14.8. To meet DOE requirements for R-38 the homeowner would likely need around 10-11 inches of open-cell insulation at an estimated cost of $5,280-$7,150. An alternative would be 6 inches of closed-cell insulation at R-39 with a cost of $9,000-$13,320 and include a vapour barrier. Compare quotes from at least two certified applicators. It is also recommended by EPA spray polyurethane foam guidance to make sure that the applicator is certified and to ensure that the space is ventilated before and after installation.