How to use it
Calculating board feet
Enter the thickness
In inches. For hardwood sold by the quarter, 4/4 is 1, 5/4 is 1.25 and 8/4 is 2. Fractions such as 3/4 or 1 3/8 work too.
Enter the width and length
Width in inches. Length in inches or feet — switch the unit under the length field, and the value already typed converts with it.
Enter the quantity
The number of boards of that size.
Add a waste allowance
Optional: a percentage for defects, end trimming and cuts. The ledger shows the net board feet, the allowance and the total to buy.
The formula
A board foot is a volume: NIST defines it as a board 1 ft long, 1 ft wide and 1 in thick — 144 cubic inches. So the board feet in any board are its volume in cubic inches divided by 144, or, with the length in feet, the thickness and width in inches times the length in feet divided by 12.
Board feet
bd ft = T × W × L(in) × qty ÷ 144
bd ft = T × W × L(ft) × qty ÷ 12
- T
- thickness (in)
- W
- width (in)
- L
- length (in or ft)
- qty
- number of boards
| Thickness (quarters) | Width | Length | Board feet |
|---|---|---|---|
| 4/4 (1 in) | 6 in | 8 ft | 1 × 6 × 8 ÷ 12 = 4 |
| 5/4 (1.25 in) | 7 in | 12 ft | 1.25 × 7 × 12 ÷ 12 = 8.75 |
| 8/4 (2 in) | 10 in | 10 ft | 2 × 10 × 10 ÷ 12 = 16.67 |
| 4/4 × 4 boards | 8 in | 96 in | 1 × 8 × 96 × 4 ÷ 144 = 21.33 |
Converting board feet
Because board feet are a volume, they convert directly only to other volumes: 1 board foot is 144 cubic inches, or 1/12 of a cubic foot. Square feet and linear feet need the dimensions that a volume does not carry, and the converter under the calculator asks for them:
- Square feet need the thickness. Square feet of face = board feet ÷ thickness (in). 12 bd ft of 3/4 in stock covers 16 sq ft; the same 12 bd ft of 1 in stock covers 12.
- Linear feet need the thickness and the width. Linear feet = board feet × 12 ÷ (thickness × width). 12 bd ft of 1 × 6 in stock is 24 linear feet.
- Without those dimensions there is no single answer, so the converter says what is missing rather than guess.
Assumptions and limits
- Nominal or actual? Hardwood is usually tallied by its rough thickness in quarters: a 4/4 board counts as 1 in thick even though, surfaced on two sides, it is about 13/16 in (Wood Handbook Table 6–4). Enter the thickness your supplier tallies by.
- Waste is your estimate. The allowance is a percentage you choose for defects, end checks and cuts; the calculator does not know your boards.
- No prices. Multiply the total by the yard’s price per board foot if you want a cost.
- Random widths. Hardwood often comes in mixed widths; add each width as its own line, or measure a bundle’s total width.
Nominal and actual sizes for softwood and hardwood are on the lumber dimensions chart. To plan the cuts once you have the boards, use the cut list optimizer.
Sources
The formula follows directly from the NIST definition of the board foot. How a particular yard tallies thickness — rough or surfaced — is the seller’s practice; ask before comparing prices.
- 1.
NIST Handbook 130 (2026), IV.B Uniform Regulation for the Method of Sale of Commodities. National Institute of Standards and Technology, 2026.
Used for: The board foot defined as the volume of a board 1 ft long, 1 ft wide and 1 in thick, or 144 cubic inches (section 2.20); hardwood lumber sold on net board footage.
- 2.
Christopher Adam Senalik and Benjamin Farber. Chapter 6: Commercial Lumber, Round Timbers, and Ties. USDA Forest Service, Forest Products Laboratory — Wood Handbook, FPL-GTR-282, 2021.
Used for: Standard rough and surfaced (S2S) hardwood thicknesses (Table 6–4) — 4/4 rough is 1 in, surfaced 13/16 in.
About this calculator
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