Board Foot Calculator – Price a Hardwood Cut List and Scale Logs
Hardwood and rough lumber are sold by the board foot, a unit of volume rather than length. This board foot calculator lets you build a complete cut list, one row per part, with its own thickness, width, length, quantity and species price. It then totals the board feet, adds a waste allowance and tells you how much lumber to buy. A second mode estimates how many board feet a sawmill can get from a log using the three common log scale rules.
The board foot formula
One board foot is a piece 12 in wide, 12 in long and 1 in thick, which is 144 in³. For any board:
Board feet = Thickness (in) × Width (in) × Length (ft) ÷ 12
= Thickness (in) × Width (in) × Length (in) ÷ 144So a board 2 in thick, 6 in wide and 12 ft long is 2 × 6 × 12 ÷ 12 = 12 board feet. In metric terms, one board foot is exactly 2,359.737216 cm³, so one cubic metre is about 423.78 board feet. One cubic foot is 12 board feet. When you choose metric input, the calculator converts millimetres, centimetres and metres to inches before applying the formula.
Quarter-sawn thickness notation
Hardwood dealers describe rough thickness in quarters of an inch. The calculator offers these as a dropdown and keeps the exact inch values, so 8/4 is always exactly 2.0 in. For other stock, pick Custom and type a decimal or a fraction such as 3/4 or 1 1/2.
| Quarters | Rough thickness | Board feet per linear foot, 6 in wide |
|---|---|---|
| 4/4 | 1 in | 0.50 |
| 5/4 | 1¼ in | 0.63 |
| 6/4 | 1½ in | 0.75 |
| 8/4 | 2 in | 1.00 |
| 12/4 | 3 in | 1.50 |
| 16/4 | 4 in | 2.00 |
Nominal versus actual size
Board feet are always worked out from the size the wood is sold as. Rough hardwood uses its rough quarter thickness, even though it will plane down thinner. Softwood dimension lumber uses its nominal size: a 2×4 is billed as 2 × 4 in, not its actual 1½ × 3½ in. Ten 8 ft 2×4s are therefore 2 × 4 × 8 ÷ 12 × 10 = 53.33 board feet. Some hardwood yards also count stock thinner than 1 in as if it were 1 in thick. Turn on the thin-stock option if your supplier bills that way.
A worked cut-list example
Suppose a small table needs a top made from three 8/4 walnut boards, 7 in wide and 6 ft long, plus four 5/4 poplar aprons, 4 in wide and 4 ft long. The walnut comes to 2 × 7 × 6 ÷ 12 × 3 = 21.00 board feet and the poplar to 1.25 × 4 × 4 ÷ 12 × 4 = 6.67 board feet, for a total of 27.67. At $14 per board foot for walnut and $5 for poplar, the wood costs $327.33 before waste. Adding 20% waste gives 33.20 board feet, so you would buy at least 34 board feet. The breakdown bar shows each row's share and the waste allowance at a glance.
Estimating lumber from a log
In Log Scale mode you enter the small-end diameter inside the bark, the log length and the number of logs. The calculator returns three estimates side by side:
- Doyle:
(D − 4)² × L ÷ 16. It is simple, but it badly under-scales small logs. - International ¼″: a polynomial that assumes a ¼ in saw kerf and allows for taper. It is the closest of the three to real mill yield.
- Scribner (approx.):
(0.79D² − 2D − 4) × L ÷ 16, a formula approximation of the diagram-based Scribner rule.
For a 16 in × 16 ft log, the calculator gives 144 board feet by Doyle, about 181 by International ¼″ and about 166 by the Scribner approximation. The raw cylinder holds about 268 board feet, and the difference is lost to slabs, edgings, sawdust and taper. The line chart shows how far Doyle falls behind the other rules below about 20 in.
Exporting your list
Copy the finished cut list as a Markdown table to paste into notes or a message, or download it as a CSV for a spreadsheet. Your list, units, waste setting and prices are saved in your browser, so the project is still there when you come back.