Hardwood lumber, live-edge slabs and many specialty softwoods are priced by the board foot, a unit of volume equal to a board 1 inch thick, 12 inches wide and 12 inches long — 144 cubic inches. The USDA Forest Products Laboratory's Wood Handbook uses this definition. This board foot calculator totals a whole cut list: enter the quantity, thickness, width and length of each line and it returns total board feet, the equivalent cubic feet and cubic metres, and the cost at your yard's price per board foot.
Construction lumber like 2×4s is usually sold by the piece or by the linear foot, but board feet are still useful for comparing prices or estimating weight. For deck and fence projects, the deck board calculator and fence calculator count pieces directly.
How to use the board foot calculator
- Add one row per size of board. Enter how many pieces, the thickness and width in inches, and the length in feet.
- For rough hardwood, enter the quarter thickness as inches: 4/4 = 1, 5/4 = 1.25, 6/4 = 1.5, 8/4 = 2, 12/4 = 3.
- For dimensional lumber, use the nominal size (a 2×4 is entered as 2 × 4). Lumber is tallied on nominal dimensions even though the dressed board is smaller.
- Enter the price per board foot to get the total cost.
Formula
Multiply by quantity for each line and add the lines. One board foot is 1/12 of a cubic foot.
Worked example
A cut list of four 1×6 boards 8 ft long, two 2×4s 10 ft long and one 8/4 walnut board 10 inches wide and 6 ft long, at $6.50 per board foot.
- 1×6×8: 1 × 6 × 8 ÷ 12 = 4 BF each, × 4 = 16 BF.
- 2×4×10: 2 × 4 × 10 ÷ 12 = 6.67 BF each, × 2 = 13.33 BF.
- 8/4 × 10 in × 6 ft: 2 × 10 × 6 ÷ 12 = 10 BF.
- Total: 16 + 13.33 + 10 = 39.33 board feet (3.28 ft³).
- Cost: 39.33 × $6.50 = $255.67.
Rough vs surfaced lumber
Hardwood dealers usually tally board feet on the rough size before planing, so a 4/4 board that measures about 13/16 inch after surfacing is still charged as 1 inch thick. Widths on random-width hardwood are measured on each board and rounded according to grading rules published by the National Hardwood Lumber Association. When you buy surfaced (S2S or S4S) stock, ask whether the price is per board foot of rough tally or of finished size.
| Quarter size | Rough thickness | Board feet per ft of a 6 in wide board |
|---|---|---|
| 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 |
Allowing for waste
Board feet measure what you buy, not what ends up in the project. Knots, checks, defects, saw kerf and planing all reduce yield. Woodworkers often buy 15–30% more than the finished cut list for hardwood, depending on the grade and how much figure-matching the project needs. Add that margin to quantities or lengths before calculating.
Caveats and assumptions
- Dimensional lumber is tallied on nominal sizes; actual dressed sizes are smaller (a 2×4 is 1½ × 3½ in).
- Some yards round lengths and widths before tallying, which can change the total slightly.
- Slabs and live-edge boards are often measured at an average width; ask how your supplier measures.
- Prices in examples are illustrative.
Frequently asked questions
What is a board foot?
A volume of wood equal to 144 cubic inches: a board 1 inch thick, 12 inches wide and 1 foot long, or any shape with the same volume.
How many board feet are in a 2×4×8?
2 × 4 × 8 ÷ 12 = 5.33 board feet, using nominal dimensions.
How do I calculate board feet with inches only?
Multiply thickness × width × length, all in inches, and divide by 144.
How many board feet in a cubic foot?
Twelve. A cubic foot is 1,728 cubic inches, and 1,728 ÷ 144 = 12.
What does 4/4 and 8/4 mean?
Hardwood thickness in quarters of an inch: 4/4 is 1 inch, 8/4 is 2 inches, measured rough before planing.
Sources
- USDA Forest Products Laboratory — Wood Handbook, Chapter 6: Commercial Lumber — board foot definition and lumber sizes
- University of Wisconsin Extension — What Is a Board Foot? — board foot calculation explained
- National Hardwood Lumber Association — Grading rules — hardwood grading and tally rules
This calculator gives estimates for planning and education. Check measurements, local codes, supplier specs and your school's official policy before relying on a result. See our disclaimer and how we build and check calculators.