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The project workbench · 02

Board-foot calculator

Build a takeoff from different surfaces and thicknesses. One board foot covers one square foot at one inch thick.

The short answer

Board feet measure volume, not thermal performance or package yield.

For each surface group, multiply net square feet by thickness in inches. Add the groups for raw board feet. Keep any planning allowance separate so it cannot be mistaken for required installed volume.

What changes the result

Check the geometry before using the total.

  • Length, width, surface count, and openings set the net area.
  • Each surface group keeps its own intended thickness.
  • Product yield, required R-value, framing, and field loss remain separate decisions.

Evidence trail

What to verify before applying this answer

Sources last checked: Sep 6, 2026. Each reference supports the point shown; it does not approve a project by itself.

  1. Volume-unit definition

    One board foot is one square foot at one inch thick. The calculator applies that geometry to each measured surface group.

    Virginia Department of Forestry: Board Foot

  2. R-value is a separate claim

    Raw board-foot volume does not establish an R-value. Use the current documented claim for the exact insulation and thickness.

    Electronic Code of Federal Regulations / Federal Trade Commission: 16 CFR 460.20: R-value per inch claims

  3. Declared yield has conditions

    A package yield depends on its stated basis and conditions. This manufacturer example does not set the yield of another product.

    DuPont: Froth-Pak Foam System Kit Instruction Manual, September 2025
Defined terms

See every source, its scope, and access date ↓

Research & references

Sources used for this guide

  1. Board FootVirginia Department of Forestry · government guidance · Customary volume-unit definition; wood-measure context, not a foam-yield guarantee · accessed
  2. 16 CFR 460.20: R-value per inch claimsElectronic Code of Federal Regulations / Federal Trade Commission · government regulation · United States; provision text checked September 6, 2026, not individualized legal advice · accessed
  3. Froth-Pak Foam System Kit Instruction Manual, September 2025DuPont · manufacturer instruction, TDS, or SDS · United States; exact-system example for yield and troubleshooting, not instructions for other formulations · accessed

A citation supports a specific statement, not every possible assembly or local code interpretation.

01

Your surface groups

Keep surfaces with different dimensions or thicknesses on separate rows.

Surface group 1

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Show the working

Simple math.
Visible assumptions.

For each group: (length × width × count − openings) × thickness

The calculator adds each raw volume, then applies your optional scenario percentage once. This keeps different walls, roof slopes, rims, or floor areas visible instead of hiding them inside one average.

Why there is no universal can or kit count

Advertised yield comes from stated test conditions. Installed yield can change with temperature, substrate, application technique, geometry, overspray, lifts, and equipment. The calculator therefore preserves raw geometry and leaves exact product conversion to current product evidence.

This calculation does not establish required R-value, account for framing thermal bridges, or set a product’s lift limit. Confirm the assembly and installation requirements before turning volume into a purchase.

Understand R-value, thickness, and board feet