Board-foot measurement and purchasing guide
A board foot is a volume of 144 cubic inches. Lumber tallies use thickness, width and length rather than floor area.
Supplier rules may use nominal or actual dimensions. Confirm the measurement and tally basis before ordering.
How to calculate board feet
- Count identical pieces: Run separate estimates for pieces with different dimensions.
- Enter the tally dimensions: Use the dimensions required by the supplier.
- Choose an allowance: Account for cuts, defects and matching requirements.
- Add price: Enter the quoted price per board foot when estimating cost.
Formula and variables
The result is increased by the selected cutting allowance before cost is calculated.
Board feet = quantity × thickness (in) × width (in) × length (ft) ÷ 12- T — Thickness
- Board thickness in inches.
- W — Width
- Board width in inches.
- L — Length
- Board length in feet.
Worked example: eight-foot boards
Ten boards measure 1 in × 6 in × 8 ft.
- Quantity
- 10
- Dimensions
- 1 in × 6 in × 8 ft
- 10 × 1 × 6 × 8 ÷ 12 = 40 board feet.
- A 10% allowance produces 44 board feet.
Result: Plan for 44 board feet.
Confirm whether the lumberyard tallies nominal or surfaced dimensions.
Understanding your results
Net board feet
Calculated volume before allowance.
Board feet to order
Net volume plus the selected cutting allowance.
Assumptions
- All entered pieces have identical dimensions.
- Price uses the same board-foot tally basis.
Limitations
- The calculator does not optimize a cut list.
- Grade, drying and surfacing are not modeled.
Common mistakes
- Dividing by 144 when length is entered in feet.
- Mixing actual and nominal dimensions.
- Forgetting defects and cuts.
Practical use cases
Lumber purchasing
Convert a material list into a supplier quantity.
Project budgeting
Apply a quoted board-foot price to the allowance-adjusted total.
Planning and decision guide
Confirm the supplier tally
Ask whether price uses nominal, rough or surfaced dimensions.
Use a project-specific allowance
Long clear cuts, grain matching and defect rates may require more material.
Frequently asked questions
What is one board foot?
A lumber volume equal to 144 cubic inches.
Is a board foot the same as a square foot?
No. A board foot measures volume; a square foot measures area.
Should I use nominal dimensions?
Use the tally basis specified by the seller or contract.
Sources and review
- Board Foot Measure — National Institute of Standards and Technology. Accessed 2026-08-03.
Reviewed 2026-08-03.