How to use the board foot calculator
- Choose U.S. or Metric measurements.
- Enter thickness and width. U.S. users can choose a rough-thickness preset, then edit it if needed.
- Enter length in feet and inches, or total length in millimetres.
- Enter the number of identical pieces in the row.
- Add another row for a different size or label.
- Open Planning to add an optional board-foot allowance, or Add pricing to enter prices per board foot.
Use the dimensions your supplier uses for board-foot tallying when checking a quote or order. Use measured dimensions when you want geometric volume from the board in front of you. This calculator uses exactly the dimensions entered.
Board foot formula
For thickness and width in inches and length in feet:
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
If all three dimensions are in inches:
Board feet = thickness (in) × width (in) × length (in) ÷ 144
One board foot is a volume of 144 cubic inches. For example, using entered dimensions of 1 in × 6 in × 8 ft: 1 × 6 × 8 ÷ 12 = 4 BF. Multiply the per-piece result by the row quantity.
What is a board foot?
A board foot measures volume, not only length or surface area. A geometric piece measuring 1 inch thick, 12 inches wide and 12 inches long contains 144 cubic inches, or one board foot. Board feet are commonly used for rough and hardwood lumber in North American trade, though lumber products are not all sold or tallied this way. The USDA Forest Service describes the same 12 × 12 × 1 inch measure and distinguishes lumber tally from log-scale rules.
Board feet vs linear feet vs square feet
- Board foot: volume, based on thickness, width and length.
- Linear foot: length along a board; the calculator reports the total length of your entered pieces.
- Square foot: area, based on two dimensions.
A linear-foot count does not determine board feet without the board's cross-section. The same is true of square footage: area alone has no thickness.
Nominal, rough and actual dimensions
Lumber dimensions may be described as nominal, rough-sawn, surfaced, finished or measured. Those labels do not always refer to the same physical dimensions. This calculator does not automatically convert nominal sizes to actual sizes. For example, enter 2 and 4 if those are the dimensions you want the geometric calculation to use; enter measured dimensions when calculating physical volume. When checking a supplier price, confirm the tally basis with that supplier.
What do 4/4, 5/4 and 8/4 mean?
In a rough-thickness notation used for hardwood lumber, the number of quarters describes a rough thickness basis in quarter-inch increments: 4/4 is 1 inch, 5/4 is 1.25 inches, 6/4 is 1.5 inches, 8/4 is 2 inches, 10/4 is 2.5 inches, 12/4 is 3 inches and 16/4 is 4 inches. The American Hardwood Export Council documents these rough thickness equivalents.
Surfacing removes material, so a finished board may be thinner than its rough thickness basis. The amount depends on the board and processing; supplier tallying practices can also vary. The presets enter rough-basis values only. They are not universal finished dimensions and do not alter width.
How to estimate lumber cost
When you know a price per board foot, estimated cost = board feet × price per board foot. A default price applies to every row unless an optional row price overrides it. Currency selection changes formatting only; it does not convert exchange rates. No current lumber prices are supplied.
If you enter an allowance, the estimate shows entered-lumber cost and planning cost separately. If any row has no price, the result shows a priced-rows subtotal and counts unpriced rows instead of presenting a complete cost.
Worked board foot example
Ten boards with entered dimensions of 1 in thick × 6 in wide × 8 ft long contain 4 BF each, or 40 BF total. At an illustrative price of $7.50/BF, the entered-lumber estimate is $300. With an illustrative 10% allowance, the planning total is 44 BF and planning cost is $330.
The 10% allowance and $7.50 price are example inputs only, not recommended or current market values. Choose any project allowance yourself and enter the prices that apply to your lumber.
Using metric measurements
Metric mode accepts thickness, width and total length in millimetres, then converts that geometry to board feet. It does not redefine a board foot. The physical equivalent of 1 in × 6 in × 8 ft is 25.4 × 152.4 × 2,438.4 mm, which is 4 BF. Results also show cubic metres; the cubic outputs represent the geometric lumber dimensions entered.
What this calculator does not calculate
This calculator uses the geometric board-foot formula for sawn lumber. It does not calculate Scribner, Doyle, International 1/4-inch or other log-scale volumes. It also does not estimate standing timber, sawmill recovery, moisture shrinkage, drying loss, saw kerf, grading, defect deductions, species value, weight or current market pricing. Log rules estimate potential lumber yield from logs under separate assumptions; they are not the formula used here.
Related material calculators
Board-foot volume does not tell you a deck-board layout, fence-post spacing or project-specific piece count. For a measured rectangular deck, use the Deck Material Calculator; for fence runs, gates and material planning, use the Fence Calculator. More material tools are in Roofing & Construction.
Read the guide to calculating board feet for a step-by-step explanation and multi-size example.
Board foot calculator questions
How do I calculate board feet?
Multiply thickness in inches by width in inches and length in feet, then divide by 12. If every dimension is in inches, divide their product by 144.
How many board feet are in a 1 × 6 × 8 board?
Using those entered dimensions, 1 × 6 × 8 ÷ 12 = 4 BF. This example does not identify a particular finished commercial board size.
Is a board foot the same as a square foot?
No. A board foot is volume; a square foot is area.
Should I use nominal or actual lumber dimensions?
Use the basis that matches your purpose. For a supplier tally, confirm the dimensions used by that supplier. For geometric volume, use measured dimensions. The calculator does not silently convert nominal values.
Can I enter metric lumber sizes?
Yes. Metric mode converts entered millimetre dimensions geometrically and returns board feet, cubic feet and cubic metres.
Does the calculator work for logs?
No. Log scaling uses separate rules and assumptions. This calculator is for sawn lumber dimensions.
Calculations run in your browser. Lumber dimensions and prices entered in this tool are not sent to a calculation server or saved in an account.
Sources: USDA Forest Service, Unit of Measure Conversion Factors for Roundwood Receiving Facilities; American Hardwood Export Council, Measurement of Sawn Lumber. The USDA Forest Products Laboratory also explains quarter-sawn grain orientation in its Wood Handbook. Sources reviewed 3 October 2026.
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