Spray Foam Insulation Calculator (Board Feet & Kits)

Converts a target R-value and area into inches of spray foam, board feet with waste, the number of kits to buy and the material cost, and compares open cell with closed cell.

For DIY buyers and contractors pricing a job.

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Results will appear here once you enter your values.

How the estimate works

The sequence is: thickness = target R / R per inch, rounded up to 0.5 in. Board feet = area x thickness. Board feet with waste = board feet x (1 + waste %). Kits = board feet with waste / kit yield, rounded up. Cost = kits x kit price.

Defaults are 1,000 sq ft, R-13, closed cell at R-6.5 per inch, 600 board feet per kit, $600 per kit and 15% waste. Thickness is 2.0 in, board feet are 2,000, and with waste 2,300. That needs 4 kits for $2,400, with 100 board feet to spare. Open cell at 3.6 per inch needs 4.0 in, 4,600 board feet with waste, 8 kits and $4,800 at the same kit price.

  • Waste: 0 to 100% for overspray and uneven substrate.
  • R per inch: edit this to match your product's data sheet.
  • Rounding: the half-inch step is a planning step, not a spray limit.

Limits of the estimate

This is a materials estimate, not an insulation design. Spray foam gives off fumes while curing, so installers and occupants should follow the manufacturer's ventilation and re-entry instructions. Some foams have fire protection requirements, and applying foam wrongly can trap moisture or cause problems.

  • Code: required R-values and coverings depend on your climate zone and local code.
  • Professional: consider a licensed installer for large areas, attics and roofs.
  • Safety: wear the protective gear listed in the kit instructions.

Sources and next steps

U.S. Department of Energy, Building America, 'Measure Guideline: Wall Air Sealing and Insulation Methods in Existing Homes' (2012), Section 3.5: open cell about R-3.6 per inch and closed cell up to R-6.5 per inch. Board foot definition: one square foot at one inch thick.

For loose-fill or batt insulation in an attic, use the attic insulation calculator. The heating load calculator shows how much a better R-value is worth, and the energy savings calculator estimates annual savings.

Frequently Asked Questions

Common questions about the Spray Foam Insulation Calculator (Board Feet & Kits)

A board foot is one square foot of area at one inch thick, so 1,000 sq ft at 2 inches is 2,000 board feet. Spray foam kits are rated by board feet of yield, for example 600. Always check the kit's rated yield, since real yield depends on temperature, thickness per pass and technique.

Sources & References

International System of Units (SI): energy, work and heat

Energy, work and heat is measured in the joule (J); 1 cal = 4.184 J. Conversions between SI and other units use exact, internationally agreed factors maintained by NIST.
→Source: NIST — International System of Units (SI)

International System of Units (SI)

Authoritative definitions for energy, work and heat, from the BIPM SI Brochure (9th edition), the defining reference for the SI.
→Source: BIPM — SI Brochure (9th ed.)

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