Spray Foam Board Foot Calculator

Multiply the area in square feet by the thickness in inches. For example, 1,500 sq ft of wall space insulated with 2 inches of foam equals 3,000 board feet (1,500 × 2 = 3,000).

No. A square foot measures area only (length × width). A board foot adds a third dimension — thickness. One board foot equals one square foot of coverage at one inch thick. So 100 sq ft at 3 inches thick = 300 board feet.

Because material usage depends on both area and thickness, not just area. A 2-inch application uses twice the material as a 1-inch application over the same area. Pricing by the board foot gives homeowners an apples-to-apples way to compare quotes.

It varies widely by project. A standard attic (1,500 sq ft at 6 inches open-cell) is about 9,000 board feet. A crawl space (800 sq ft at 2 inches closed-cell) is about 1,600 board feet. Exterior walls (1,200 sq ft at 3 inches) are about 3,600 board feet.