Quick answer: board feet = thickness (in) × width (in) × length (ft) ÷ 12. A 2×6 that is 10 ft long is 2 × 6 × 10 ÷ 12 = 10 board feet. With the length in inches, divide by 144.
What is a board foot?
A board foot (BF or bd ft) is the standard unit of volume for lumber in the US and Canada: a piece 1 in thick, 12 in wide and 12 in long, or 144 cubic inches. Any shape with the same volume is also one board foot, for example 2 in × 6 in × 12 in. Hardwood dealers price almost everything by the board foot, and softwood is often priced that way in bulk.
Board foot formulas
BF = T (in) × W (in) × L (ft) ÷ 12 · BF = T × W × L (in) ÷ 144
Multiply by the quantity for several identical boards, and by the price per board foot for the cost. The calculator does each row and adds them up, so you can enter a whole cut list.
Board feet chart for common lumber
Board feet per piece for common nominal sizes and lengths.
| Size | 8 ft | 10 ft | 12 ft | 16 ft |
|---|---|---|---|---|
| 1×4 | 2.67 | 3.33 | 4.00 | 5.33 |
| 1×6 | 4.00 | 5.00 | 6.00 | 8.00 |
| 1×8 | 5.33 | 6.67 | 8.00 | 10.67 |
| 1×10 | 6.67 | 8.33 | 10.00 | 13.33 |
| 1×12 | 8.00 | 10.00 | 12.00 | 16.00 |
| 2×4 | 5.33 | 6.67 | 8.00 | 10.67 |
| 2×6 | 8.00 | 10.00 | 12.00 | 16.00 |
| 2×8 | 10.67 | 13.33 | 16.00 | 21.33 |
| 2×10 | 13.33 | 16.67 | 20.00 | 26.67 |
| 2×12 | 16.00 | 20.00 | 24.00 | 32.00 |
| 4×4 | 10.67 | 13.33 | 16.00 | 21.33 |
| 6×6 | 24.00 | 30.00 | 36.00 | 48.00 |
Nominal vs actual size
Softwood boards are named by their rough size before drying and planing, so a 2×4 actually measures 1½ × 3½ in. Lumber yards still calculate board feet from the nominal size for softwood dimensional lumber. Pick “Measured / hardwood” when you are buying by the true dimensions.
| Nominal | Actual | Nominal | Actual |
|---|---|---|---|
| 1×2 | ¾ × 1½ in | 2×4 | 1½ × 3½ in |
| 1×3 | ¾ × 2½ in | 2×6 | 1½ × 5½ in |
| 1×4 | ¾ × 3½ in | 2×8 | 1½ × 7¼ in |
| 1×6 | ¾ × 5½ in | 2×10 | 1½ × 9¼ in |
| 1×8 | ¾ × 7¼ in | 2×12 | 1½ × 11¼ in |
| 1×12 | ¾ × 11¼ in | 4×4 | 3½ × 3½ in |
Buying hardwood by the board foot
Hardwood is sold rough or surfaced, in random widths and lengths. The thickness is given in quarters of an inch, measured before surfacing:
| Quarters | Rough thickness (used for BF) | Typical surfaced (S2S) |
|---|---|---|
| 4/4 | 1 in | ≈ 13⁄16 in |
| 5/4 | 1¼ in | ≈ 1 1⁄16 in |
| 6/4 | 1½ in | ≈ 1 5⁄16 in |
| 8/4 | 2 in | ≈ 1¾ in |
To estimate, add up the board feet in your cut list, then add a generous allowance for defects and yield. Many woodworkers add 20–30% for furniture.
Worked examples
A stack of 2×6s
Twelve 2×6 × 10 ft: 2 × 6 × 10 ÷ 12 × 12 = 120 board feet. At $1.20 per board foot, $144.
Hardwood for a table top
Five boards of 5/4 walnut, 6 in wide and 8 ft long: 1.25 × 6 × 8 ÷ 12 = 5 BF each, 25 BF total; with 25% extra, buy about 31 BF.
Length in inches
A 1 × 8 × 30 in shelf: 1 × 8 × 30 ÷ 144 = 1.67 BF. Set “Length in” to inches.
Conversions
- 1 board foot = 144 cubic inches = 1/12 cubic foot = 0.00236 m³ (2.36 liters).
- 1 cubic foot = 12 board feet. 1 m³ ≈ 424 board feet.
- 1,000 board feet is written MBF; log and timber prices are often per MBF.
- Linear feet: for a given width and thickness, BF per linear foot = T × W ÷ 12 (a 2×4 is 0.667 BF per foot).
How to measure rough lumber
- Thickness: read the quarter size on the stack (4/4, 8/4…) or measure the rough board.
- Width: measure across the narrowest full-thickness part, ignoring bark (wane) on the edges. Dealers usually round to the nearest inch.
- Length: measure to the nearest foot, rounding down, unless the dealer rounds differently.
- Calculate each board and add them up. Enter each board as a row in the calculator.
Comparing prices per piece and per board foot
Stores price the same lumber in different ways. Convert everything to dollars per board foot to compare:
| Piece | Board feet | If it costs $10 |
|---|---|---|
| 1×6 × 8 ft | 4.00 | $2.50 per BF |
| 1×12 × 8 ft | 8.00 | $1.25 per BF |
| 2×4 × 8 ft | 5.33 | $1.88 per BF |
| 2×6 × 10 ft | 10.00 | $1.00 per BF |
| 4×4 × 8 ft | 10.67 | $0.94 per BF |
Common mistakes
- Mixing inches and feet for the length; divide by 12 for feet, 144 for inches.
- Using surfaced thickness for hardwood priced by rough quarters.
- Forgetting yield: you can’t use every inch; knots, checks and planing all cost wood.
Notes for woodworkers and estimators
Random widths. Measure each rough board’s width to the nearest inch (the dealer usually rounds), multiply by its length and thickness, and sum.
Surface measure. For 1 in stock, board feet equal the surface area in square feet. Thicker stock: multiply by thickness.
Price per piece. Big-box stores price per piece. Convert to $/BF to compare: price ÷ BF of the piece.
Rounding. NHLA rules and yards round lengths and widths; expect small differences from a calculator.
Tips
- Need to plan cuts? The lumber calculator works out how many boards to buy for a cut list.
- Framing a wall? Use the framing calculator.
- Send the list to the lumber yard with WhatsApp or Email under the result.
Frequently asked questions
How do I calculate board feet?
Multiply thickness (in) × width (in) × length (ft) and divide by 12. A 2×6 that is 10 ft long has 2 × 6 × 10 ÷ 12 = 10 board feet. If the length is in inches, divide by 144 instead.
What is a board foot?
A board foot is a volume of wood 12 in × 12 in × 1 in, which is 144 cubic inches or 1/12 of a cubic foot. Hardwood and some softwood lumber is priced per board foot.
Do I use nominal or actual size for board feet?
For softwood dimensional lumber (2×4, 2×6…), lumber yards use the nominal size, so a 2×4 counts as 2 in × 4 in even though it measures 1½ × 3½ in. For hardwood, the thickness is the rough “quarter” size (4/4 = 1 in, 8/4 = 2 in) and the width is measured. The calculator lets you choose.
How many board feet are in a 2×4×8?
2 × 4 × 8 ÷ 12 = 5.33 board feet, using nominal size.
What does 4/4 or 8/4 mean?
Hardwood thickness in quarters of an inch: 4/4 (“four quarter”) is 1 in rough, 5/4 is 1¼ in, 6/4 is 1½ in and 8/4 is 2 in. Board feet use these rough thicknesses.
How many board feet are in a cubic foot?
Twelve. A cubic foot is 12 × 12 × 12 in, and a board foot is 12 × 12 × 1 in.
How do I convert price per board foot to price per piece?
Multiply the board feet in the piece by the price per board foot. A 1×6 × 8 ft is 4 board feet, so at $5.50 per board foot it costs $22.
How much extra should I buy?
For furniture and cabinets, buyers commonly add 15–30% to the board feet in the cut list for defects, knots and grain matching. For simple framing or shelving, 10% is usually enough.
Is this board foot calculator free to use online?
Yes. The CalcWall Board Foot Calculator is completely free and works online in any browser, on a phone, tablet or computer. There is nothing to download and no account to create, and the math runs right in your browser, so results appear as you type.