Lumber Calculator
Calculate board feet and the cost of lumber for a project.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
A board foot is 144 cubic inches. This calculator accepts thickness and width in inches and length in feet, so it converts the length to inches before calculating board feet. The estimate uses the dimensions you enter; nominal lumber sizes may differ from actual dressed dimensions.
Worked example
calculated with the default values below
Nominal thickness 2 in · Nominal width 6 in · Length per piece 8 ft · Number of pieces 10 · Price per board foot 6 $ Board feet per piece 8.00 bf · Total board feet 80.00 bf · Total linear feet 80.0 ft · Total cost 480.00 $
General background references
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
BF = T × W × (12L) ÷ 144; BF_total = BF × Q; linearFeet = L × Q; cost = BF_total × p
- T
- thickness (in)
- W
- width (in)
- L
- length per piece (ft)
- Q
- pieces
- BF
- board feet
- p
- price per board foot
Length is entered in feet and converted to inches before dividing cubic inches by 144. A 2 × 6 × 8 ft piece is 8 board feet.
Frequently asked questions
How is board footage calculated when length is entered in feet?
Thickness and width are in inches, while length is in feet. The calculator converts length to inches and divides the resulting cubic inches by 144. A 2 × 6 × 8 ft piece is 8 board feet; 10 pieces total 80 board feet. At $6 per board foot, the estimate is $480. This uses the entered nominal dimensions; confirm the supplier’s pricing basis.