Quick answer
Board feet = thickness (in) × width (in) × length (ft) ÷ 12. A 2 × 4 inch board 8 feet long is 5.3333 board feet.
Enter thickness, width, length and pieces. The calculator returns total board feet. Use this board foot calculator to check your own figures.
Related tools: Square Footage Calculator: Area of a rectangular space in square feet, square metres and square yards. Concrete Calculator: Cubic yards of concrete for a slab, plus bag counts. Gravel Calculator: Cubic yards of gravel for an area.
How to use the Board Foot Calculator
- Enter thickness (in) (above 0).
- Enter width (in) (above 0).
- Enter length (ft) (above 0).
- Optionally, enter pieces (a whole number, 1 or more). It starts at 1.
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Thickness | A number, in in | > 0 |
| Width | A number, in in | > 0 |
| Length | A number, in ft | > 0 |
| Pieces (optional) | A whole number | ≥ 1, starts at 1 |
Formula and method
Formula
board feet = thickness (in) × width (in) × length (ft) ÷ 12
IEEE-754 double precision; shown to at most 6 decimal places.
One board foot is 144 cubic inches of nominal lumber.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Thickness = 2; Width = 4; Length = 8; Pieces = 1.
| Result | Value |
|---|---|
| Board feet | 5.3333 bd ft |
Example 2
Inputs: Thickness = 1; Width = 12; Length = 10; Pieces = 5.
| Result | Value |
|---|---|
| Board feet | 50 bd ft |
The first line is the headline result (board feet). IEEE-754 double precision; shown to at most 6 decimal places.
What a board foot is
One board foot is a piece 1 inch thick, 12 inches wide and 12 inches long (144 cubic inches). Hardwood is sold this way. At $6 per board foot the 2 × 4 above costs $32.
Nominal versus actual
The calculator uses the dimensions you enter. A softwood '2 × 4' is really 1.5 × 3.5 inches, which would be 3.5 board feet at 8 ft, so enter the size the seller bills on.
How the result changes with thickness
Holding every other input at the first worked example, this table changes only thickness. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Thickness | Board feet |
|---|---|
| 1 | 2.6667 bd ft |
| 2 | 5.3333 bd ft |
| 4 | 10.6667 bd ft |
| 8 | 21.3333 bd ft |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Thickness: entering "0" shows "Thickness must be greater than 0." beside that field and no result.
Choosing between the Board Foot Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Square Footage Calculator](/construction/square-footage-calculator/) | length, width and unit | Area |
| [Concrete Calculator](/construction/concrete-calculator/) | length, width and depth / thickness | Cubic yards |
| [Gravel Calculator](/construction/gravel-calculator/) | length, width and depth / thickness | Cubic yards |
| [Mulch Calculator](/construction/mulch-calculator/) | length, width and depth / thickness | Cubic yards |
| [Soil Calculator](/construction/soil-calculator/) | length, width and depth / thickness | Cubic yards |
Background: construction estimates
Material quantities are geometry plus a margin. Calculate the exact volume or area, add an allowance for waste, spillage, cuts and uneven ground (calculator pages commonly mention 5 to 10 percent, a rule of thumb that varies by material and job) and round up to whole units. One cubic yard is exactly 27 cubic feet.
Suppliers often have minimum order sizes and may charge for small loads, so confirm quantities, product yields and local code with your supplier or a qualified estimator before ordering.
Assumptions and limitations
- Uses nominal dimensions as entered
Quantities are estimates. Add allowances for waste and site conditions, and follow local codes and a qualified professional's instructions for structural or safety-critical work.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for thickness to confirm this.
Frequently asked questions
How many board feet in a 1 × 12 × 8?
A 1 × 12 × 8 board is 8 board feet.
Is board foot a volume?
Yes, 1/12 cubic foot.
How do I price lumber?
Multiply board feet by the price per board foot.
What does the Board Foot Calculator calculate?
Board feet of lumber from thickness, width and length. It returns Board feet.
What formula does the Board Foot Calculator use?
board feet = thickness (in) × width (in) × length (ft) ÷ 12. One board foot is 144 cubic inches of nominal lumber.
What do I need to enter in the board Foot Calculator?
You enter Thickness (in), Width (in) and Length (ft). Optional: Pieces.
How is the result rounded or limited?
IEEE-754 double precision; shown to at most 6 decimal places. Uses nominal dimensions as entered.
What is an example of a board Foot result?
With thickness 2, width 4, length 8 and pieces 1, the board feet is 5.3333 bd ft.
Can I rely on this calculator for a decision?
Quantities are estimates. Add allowances for waste and site conditions, and follow local codes and a qualified professional's instructions for structural or safety-critical work. For this calculator in particular: Uses nominal dimensions as entered.
Related calculators
- Square Footage Calculator — Area of a rectangular space in square feet, square metres and square yards.
- Concrete Calculator — Cubic yards of concrete for a slab, plus bag counts.
- Gravel Calculator — Cubic yards of gravel for an area.
- Mulch Calculator — Cubic yards of mulch for a bed.
- Soil Calculator — Cubic yards of soil for an area.
- Sand Calculator — Cubic yards of sand for an area.
- Paint Calculator — Gallons of paint for the walls of a room.
- Brick Calculator — Bricks and mortar volume for a wall.
- Board and Batten Layout Calculator — Number of boards and the real gap for an even board-and-batten or panel layout.
Sources
- OpenStax, University Physics Volume 1 (Rice University): mechanics
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.