Free spray foam and blown-in insulation calculators

Use this free spray foam board foot calculator to get board feet, sets to order and material cost for open-cell or closed-cell foam. Switch to the blown-in insulation bag calculator to count bags for an attic. Both stay free. Need to measure a whole plan? Try the InsulBid takeoff tool.

Area (sq ft)

Thickness (inches)

Foam type

Yield per set (bd ft)Use your manufacturer's data sheet

Roof pitchOnly if the area is the floor footprint of a sloped deck

Framing deduction (%)Studs/rafters not sprayed, often 0–15%

Waste / overspray (%)

Price per set ($, optional)

Spray area–

Board feet–

With waste–

Sets needed–

Material cost–

Board feet = sq ft × inches of thickness. Yield depends on product, temperature and substrate, so treat this as an estimate.

How it's calculated

What is a board foot of spray foam?

One board foot is 1 sq ft of foam, 1 inch thick. So 1,000 sq ft sprayed 3" thick is 3,000 board feet.

How many sets of spray foam do I need?

Divide the board feet (with waste) by your product's yield per set. Closed-cell sets usually yield a few thousand board feet, and open-cell sets yield much more. Check the data sheet, because yield changes with temperature and substrate.

How does roof pitch change the area?

If you measured the floor footprint under a sloped roof deck, the sloped surface is bigger. The calculator multiplies by √(1 + (rise/12)²). For example, a 12/12 roof has about 1.41× the footprint area.

How many bags of blown-in insulation do I need?

Take the attic floor area, add waste, and divide by the coverage per bag shown on the bag's chart for your target R-value. Round up to whole bags.