What is a board foot?
A board foot is a unit of lumber volume: a piece 1 in thick, 12 in wide and 12 in long, or 144 cubic inches. Hardwood and rough-sawn lumber are usually priced per board foot, so knowing the total lets you compare prices and budget a project accurately.
Board foot formula
If every dimension is in inches, divide by 144 instead. Multiply by the number of boards for the total.
Worked example
Ten boards 1 in thick, 6 in wide and 8 ft long: 1 × 6 × 8 ÷ 12 = 4 board feet each, or 40 board feet in total. At $6.50 per board foot, that is $260.
Nominal vs actual size
Softwood construction lumber is sold by its nominal size — a 2×4 actually measures 1½ × 3½ in after drying and planing. Board feet for dimensional lumber are traditionally calculated with nominal sizes, which is what lumber yards use for pricing.
Hardwood is described by thickness in quarters of an inch: 4/4 ("four quarter") is 1 in thick rough, 5/4 is 1¼ in, 6/4 is 1½ in and 8/4 is 2 in. Rough hardwood is measured at its rough thickness; if you are buying surfaced (S2S or S4S) stock, ask whether the price is based on rough or finished dimensions.
Board foot chart
Board feet for common nominal sizes:
| Nominal size (in) | Per linear foot | 8 ft board | 10 ft board | 12 ft board |
|---|---|---|---|---|
| 1 × 4 | 0.333 | 2.67 | 3.33 | 4.00 |
| 1 × 6 | 0.500 | 4.00 | 5.00 | 6.00 |
| 1 × 8 | 0.667 | 5.33 | 6.67 | 8.00 |
| 2 × 4 | 0.667 | 5.33 | 6.67 | 8.00 |
| 2 × 6 | 1.000 | 8.00 | 10.00 | 12.00 |
| 2 × 8 | 1.333 | 10.67 | 13.33 | 16.00 |
| 2 × 10 | 1.667 | 13.33 | 16.67 | 20.00 |
| 2 × 12 | 2.000 | 16.00 | 20.00 | 24.00 |
| 4 × 4 | 1.333 | 10.67 | 13.33 | 16.00 |
How much extra to buy
- Allow 15–20% extra for furniture and cabinetry in hardwood — knots, checks, sapwood and grain matching all create waste.
- Allow about 10% for framing and general carpentry.
- Buy a few longer boards than you strictly need; it is easier to cut down than to join.
Plan the whole job
Framing stairs? Get stringer and tread sizes from the stair calculator. Building a wood fence? The fence calculator counts posts, rails and pickets to price by the board foot.
Frequently asked questions
How do you calculate board feet?
Multiply thickness (in) × width (in) × length (ft) and divide by 12. A 2 × 6 that is 10 ft long is 2 × 6 × 10 ÷ 12 = 10 board feet.
How many board feet are in a 2×4×8?
Using nominal dimensions, a 2×4 that is 8 ft long contains 5.33 board feet.
How many board feet are in a cubic foot?
12. A cubic foot is 1,728 cubic inches and a board foot is 144 cubic inches, so 1,728 ÷ 144 = 12.
Do I use nominal or actual dimensions?
For softwood dimensional lumber, use nominal sizes — that is how it is priced. For rough hardwood, use the rough-sawn thickness (4/4, 8/4 and so on) and actual width.
What is the difference between a board foot and a linear foot?
A linear foot measures length only, regardless of size. A board foot measures volume, so a 2×12 has six times as many board feet per linear foot as a 1×4.
Sources & standards
This calculator's formulas and default values are based on the following codes, standards and published data. Codes are adopted and amended locally, so check with your building department for permitted work. See how we build and check our calculators.
- National Hardwood Lumber Association (NHLA) Rules for the Measurement & Inspection of Hardwood: board foot measurement and quarter-inch (4/4, 8/4) thickness.
- American Softwood Lumber Standard (NIST/DOC PS 20): nominal versus dressed lumber sizes.
- Definition: 1 board foot = 144 in³ (12 × 12 × 1 in).