How this calculator works
The spray foam insulation cost calculator starts with the area you plan to insulate and the foam depth in inches. It multiplies those numbers to get board feet.
DAP defines a board foot as a 12 in by 12 in square at 1 in thick. In plain terms, 1 square foot sprayed 1 inch thick is 1 board foot. If you spray the same square foot 2 inches thick, you need 2 board feet.
The calculator then adds any extra allowance you enter for yield loss, overspray, uneven depth, or trimming. It multiplies those order board feet by your price per board foot and adds any fixed project cost.
Spray foam cost formula
Start with board feet:
Board feet = area in square feet x foam depth in inchesThen add your extra allowance:
Order board feet = board feet x (1 + extra percent / 100)The foam cost is:
Foam cost = order board feet x price per board footThe final estimate is:
Total cost = foam cost + fixed project costSay you plan to spray 500 sq ft at 2 in thick. Your quote or kit math comes out to $1.50 per board foot, and you add 10% extra.
500 x 2 = 1,000 board ft
1,000 x 1.10 = 1,100 board ft to price
1,100 x $1.50 = $1,650If there is no fixed project cost, the estimate is $1,650.
Board feet by area and depth
These examples are before extra allowance. Multiply by your price per board foot to estimate the foam portion of the job.
| Area | 1 in depth | 2 in depth | 3 in depth |
|---|---|---|---|
| 100 sq ft | 100 board ft | 200 board ft | 300 board ft |
| 250 sq ft | 250 board ft | 500 board ft | 750 board ft |
| 500 sq ft | 500 board ft | 1,000 board ft | 1,500 board ft |
| 1,000 sq ft | 1,000 board ft | 2,000 board ft | 3,000 board ft |
DAP notes that theoretical yield is measured under ideal conditions and actual output can change with temperature, humidity, application method, and application type. DuPont also lists Froth-Pak kits by board-foot yield, such as a 200 board foot kit.
How to enter price
Use the price per board foot from your installer quote when you have one. That may already include labor, equipment, travel, and overhead. If it does, leave fixed project cost at $0.
For a DIY kit, divide the kit price by the rated board-foot yield:
Price per board foot = kit price / kit board-foot yieldThen enter the kit yield if you want a kit count. For example, a kit rated at 200 board feet needs 3 kits for a 504 board foot order.
You can also use the Interior Painting Cost Calculator for finish work, the Drywall Calculator for panel estimates, or the Roof Square Footage Calculator for roof area planning.
Safety and limitations
This is a cost estimate, not an installation plan. It does not choose open-cell or closed-cell foam, set R-value targets, check vapor retarder rules, or decide whether a surface is safe to spray.
EPA says only workers wearing appropriate PPE should be present during spray polyurethane foam installation, and safe re-entry depends on product formulation and curing conditions. Follow the product label, safety data sheet, local code, and installer instructions.
Actual cost can change because of access, prep, masking, ventilation, cleanup, lift or crawl-space work, minimum trip charges, removal of old insulation, fire coating, and local labor rates.