Board Foot Calculator
A board foot is a volume: 144 cubic inches, a board 1 inch thick, 12 inches wide and 1 foot long. Lumber yards and sawmills price hardwood, rough-sawn stock and large orders of framing by the board foot, so turning a lumber list into board feet is how you compare quotes. Enter the thickness and width in inches, the length in feet and how many pieces, and this gives the board feet per piece, the total, the cubic feet and the cost.
What a board foot is
A board foot is 144 cubic inches of wood — a piece 1 inch thick, 12 inches wide and 1 foot long (USDA Forest Products Laboratory, Wood Handbook). Thickness and width go in inches, length in feet, and the product is divided by 12. Softwood framing lumber is counted on its nominal size under the American Softwood Lumber Standard (PS 20), so a 2x6 is tallied as 2 × 6 even though it measures 1½ × 5½ in when dry.
Board feet in common deck lumber
| Size | 8 ft | 10 ft | 12 ft | 16 ft |
|---|---|---|---|---|
| 2x4 | 5.33 | 6.67 | 8 | 10.67 |
| 2x6 | 8 | 10 | 12 | 16 |
| 2x8 | 10.67 | 13.33 | 16 | 21.33 |
| 2x10 | 13.33 | 16.67 | 20 | 26.67 |
| 2x12 | 16 | 20 | 24 | 32 |
| 4x4 | 10.67 | 13.33 | 16 | 21.33 |
| 6x6 | 24 | 30 | 36 | 48 |
| 5/4x6 decking | 5 | 6.25 | 7.5 | 10 |
Worked example: joists for a 12 x 16 deck
| Step | Working | Result |
|---|---|---|
| Joists at 16 in on centre across 16 ft | 16 × 12 ÷ 16 + 1 | 13 joists |
| Board feet per 2x8x12 | 2 × 8 × 12 ÷ 12 | 16 bf |
| All joists | 13 × 16 | 208 bf |
| Cubic feet | 208 ÷ 12 | 17.3 cu ft |
| At $0.90 per board foot | 208 × 0.90 | $187.20 |
Hardwood and rough lumber
Hardwood (ipe, oak, walnut) is sold on its actual rough size, in quarters of an inch: 4/4 is 1 in thick, 5/4 is 1¼ in, 8/4 is 2 in. A rough 5/4 board 6 in wide and 8 ft long is 1.25 × 6 × 8 ÷ 12 = 5 board feet. Surfaced hardwood loses thickness in the planer, but the yard still bills the rough tally.
Turning board feet into a deck? The deck materials calculator builds the whole lumber list, the deck framing calculator sizes the joists, beams and posts, and the square feet to linear feet calculator converts deck area into running feet of decking.
Get the Smart Decking Calculator app for Android
Estimate decks on the go, save projects, and share them with contractors.
Building something else? Try our sister calculators
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Frequently asked questions
- How do you calculate board feet?
- Multiply the thickness in inches by the width in inches by the length in feet, then divide by 12. A 2x6 that is 12 ft long is 2 × 6 × 12 ÷ 12 = 12 board feet. If you measure the length in inches, divide by 144 instead.
- How many board feet is a 2x4x8?
- 5.33 board feet: 2 × 4 × 8 ÷ 12. Softwood lumber is counted on its nominal size, so the fact that a dry 2x4 is really 1½ × 3½ in does not change the tally.
- Do you use actual or nominal size for board feet?
- For softwood dimension lumber (2x4, 2x6, 4x4 and so on), the nominal size, under the American Softwood Lumber Standard. For hardwood, the actual rough size, measured in quarters of an inch: 4/4 is 1 in thick, 5/4 is 1¼ in and 8/4 is 2 in.
- How many board feet are in a cubic foot?
- Twelve. A board foot is 144 cubic inches and a cubic foot is 1,728 cubic inches, so 1,728 ÷ 144 = 12. A thousand board feet (1 MBF) is 83.3 cubic feet.
- What is the price per board foot?
- Divide the price of a board by its board feet. A 2x8x16 is 21.33 board feet, so at $18 it costs about $0.84 a board foot. Comparing that figure across sizes shows which is really cheaper.
