How to use board feet calculator
What this calculation does
A board foot is a lumber quantity measure whose meaning depends on whether the entered dimensions are actual geometry or a nominal sale basis.
Choose a calculation mode and unit system, select the dimension basis where offered, then enter dimensions and quantity for each board group.
Enter the measurements
- Calculation: Choose matching board dimensions or finished-part-to-rough-stock mode.
- Input units: Choose inches and feet or the supported metric input units.
- Dimension basis: Select the dimension convention used by the product or quote; do not mix nominal labels with measured geometry.
- Thickness: Measure thickness or use the quoted nominal thickness.
- Width: Measure width or use the quoted nominal width.
- Length: Enter board length in feet.
- Number of boards: Count boards in this dimension group.
- Finished thickness: For rough-stock mode, enter finished thickness.
- Finished width: For rough-stock mode, enter finished width.
- Finished length: For rough-stock mode, enter finished length in inches.
- Total thickness allowance: Add the full thickness milling allowance.
- Total width allowance: Add the full width milling allowance.
- Total length allowance: Add the full length milling allowance.
Formula and variables
Actual geometric BF = thickness (in) × width (in) × length (ft) × quantity ÷ 12. Softwood nominal board measure uses the same arithmetic with nominal thickness and width. Rough stock dimensions add the total user-entered milling allowance before calculating.
For inch thickness and width with length in feet, BF = thickness×width×length×quantity÷12. Metric entries convert to these basis units; rough-stock mode adds each user allowance first.
Read the result
One nominal 2×4×8 ft board calculates to 5.333 nominal board feet. This is not its actual geometric volume.
Worked example
Inputs: 2 in × 4 in × 8 ft, 1 nominal softwood board
- 2×4×8÷12 = 5.3333 BF per board.
- For one board, total = 5.3333×1 ≈ 5.333 BF.
Expected result: 5.333 nominal board feet
Frequently asked questions
Why can nominal and actual results differ?
Nominal dimensions describe a product or sale basis; actual dimensions describe physical geometry. Keep the chosen basis explicit.
Does this determine a seller’s invoice tally?
No. Confirm the applicable product and transaction method with the seller.
Conditions, presets and technical notes
Actual measured dimensions produce a geometric quantity based on 144 cubic inches per board foot. Softwood nominal board measure uses nominal thickness, nominal width and length; it is not the same as actual physical volume. Hardwood sale and tally methods vary by product and transaction. Enter the basis stated by the product or quote. This is an estimate, not a sale-compliance determination.
All board groups share one unit system and dimension basis. A unit switch converts the entered dimensions.
Actual uses measured dimensions for physical volume. Nominal uses entered trade sizes; for softwood, that is nominal board measure, not physical volume. Hardwood tally conventions may differ.