Hardwood and many specialty lumber yards sell by the board foot, a volume unit equal to a board 1 inch thick, 12 inches wide and 12 inches long (144 in³). Knowing the board footage lets you compare prices between yards, check an invoice and plan how much rough stock to buy for a project. Use the nominal thickness for rough-sawn stock (a 4/4 board counts as 1 inch) and the actual size for anything else.
How to use the Board Foot Calculator
- Thickness — Use quarters for rough lumber: 4/4 = 1 in, 5/4 = 1.25 in, 8/4 = 2 in
- Width
- Length
- Number of pieces
- Waste allowance
- Price per board foot
- Every result field is editable: type into Total board feet or any other result and Length plus every other field update to match.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Multiply thickness and width in inches by the length in feet and divide by 12. Multiply by the number of pieces, add a waste allowance for defects and offcuts, then multiply by the price per board foot.
Board feet in common sizes (per 8 ft length)
| Nominal size | Board feet per foot | Board feet in 8 ft |
|---|---|---|
| 1×4 | 0.333 | 2.67 |
| 1×6 | 0.5 | 4 |
| 1×8 | 0.667 | 5.33 |
| 2×4 | 0.667 | 5.33 |
| 2×6 | 1 | 8 |
| 2×8 | 1.33 | 10.7 |
| 2×10 | 1.67 | 13.3 |
| 2×12 | 2 | 16 |
| 4×4 | 1.33 | 10.7 |
| 6×6 | 3 | 24 |
Tips for an accurate estimate
- Measure every dimension twice and write the unit next to each number – most estimating errors are unit mix-ups (inches entered as feet).
- Pick the unit in each field’s menu instead of converting by hand; the calculator converts everything to the same base before it multiplies.
- Round up only at the very end. Rounding each dimension first can add several percent to the final quantity.
- Suppliers sell in whole units – bags, boxes, sheets or quarter yards – so always round the final order up, not down.
Common mistakes to avoid
- Mixing square and cubic units: square feet measure area, cubic yards measure volume, and you need a depth to go from one to the other.
- Using nominal lumber sizes where actual sizes matter (a 2×4 is really 1½ × 3½ in).
- Forgetting that 1 yd³ = 27 ft³, not 9 ft³ (9 is for square yards).
Inputs explained
| Field | What to enter |
|---|---|
| Thickness | Units: in, cm, mm, ft, m. Use quarters for rough lumber: 4/4 = 1 in, 5/4 = 1.25 in, 8/4 = 2 in |
| Width | Units: in, cm, mm, ft, m |
| Length | Units: ft, m, in, yd, cm |
| Number of pieces | A number |
| Waste allowance | In % |
| Price per board foot | Units: /board ft, /m³, /ft³ |
What each result means
- Board feet per piece = [Thickness]×[Width]×[Length]
- Total board feet = [Thickness]×[Width]×[Length]×[Number of pieces]
- Board feet to buy (with waste) = [Total board feet]×(1 + [Waste allowance]÷100)
- Total linear feet = [Length]×[Number of pieces]
- Estimated cost = [Board feet to buy (with waste)]×[Price per board foot]
Formula
Board feet = thickness (in) × width (in) × length (ft) ÷ 12Total = board feet per piece × pieces × (1 + waste)Cost = total board feet × price per board footWorked example
Inputs — Thickness: 1 in; Width: 6 in; Length: 8 ft; Number of pieces: 10; Waste allowance: 15 %; Price per board foot: $6.5 /board ft.
Results — Board feet per piece = 4 board ft; Total board feet = 40 board ft; Board feet to buy (with waste) = 46 board ft; Total linear feet = 80 ft; Estimated cost = $299.00.
Key terms
- Board foot
- A volume of 144 cubic inches (1 in × 12 in × 12 in), about 2.36 litres.
- Nominal size
- The rough-sawn size used to name lumber; a nominal 2×4 is actually 1½ × 3½ in after drying and planing.
Frequently asked questions
How many board feet are in a 2×4 that is 8 feet long?
2 × 4 × 8 ÷ 12 = 5.33 board feet using nominal sizes. Lumber yards selling dimensional lumber by the piece usually ignore board feet, but hardwood dealers price by them.
What is 4/4, 5/4 and 8/4 lumber?
Rough hardwood thickness in quarter inches: 4/4 is 1 in, 5/4 is 1¼ in, 6/4 is 1½ in and 8/4 is 2 in. Use these nominal numbers for board feet.
How many board feet are in a cubic foot?
Twelve, because a cubic foot is 1,728 in³ and a board foot is 144 in³.
Why add waste?
Knots, checks, snipe and offcuts usually cost 15–30% of rough hardwood; furniture makers often allow even more.
What formula does the Board Foot Calculator use?
Board feet = thickness (in) × width (in) × length (ft) ÷ 12.