Board Foot Calculator
Board feet from thickness, width, length and quantity, with cost per board foot, nominal vs actual sizes explained and a table of common dimensional lumber.
Board Foot Calculator: with the default inputs, board feet is 40.
Nominal for softwood (a 2×4 is 2). Hardwood in quarters: 4/4 = 1 in, 5/4 = 1.25, 8/4 = 2.
Nominal for dimensional lumber; actual measured width for random-width hardwood.
- Board feet per piece
- 4
- Total linear feet
- 80 ft
- Cubic feet of wood
- 3.333Board feet ÷ 12.
- Cost
- $0.00
Assumptions
- Board feet are calculated on the dimensions you enter — use nominal sizes for softwood and rough thickness for hardwood, as dealers do.
- No rounding to the nearest board foot per piece; tallies at a yard may round each board.
| Nominal | Actual (in) | Board ft per linear ft | Board ft, 8-ft piece |
|---|---|---|---|
| 1 × 2 | ¾ × 1½ | 0.167 | 1.33 |
| 1 × 4 | ¾ × 3½ | 0.333 | 2.67 |
| 1 × 6 | ¾ × 5½ | 0.5 | 4 |
| 1 × 8 | ¾ × 7¼ | 0.667 | 5.33 |
| 1 × 12 | ¾ × 11¼ | 1 | 8 |
| 2 × 4 | 1½ × 3½ | 0.667 | 5.33 |
| 2 × 6 | 1½ × 5½ | 1 | 8 |
| 2 × 8 | 1½ × 7¼ | 1.333 | 10.67 |
| 2 × 10 | 1½ × 9¼ | 1.667 | 13.33 |
| 2 × 12 | 1½ × 11¼ | 2 | 16 |
| 4 × 4 | 3½ × 3½ | 1.333 | 10.67 |
| 6 × 6 | 5½ × 5½ | 3 | 24 |
Actual sizes per the American Softwood Lumber Standard (PS 20) for dry, surfaced lumber. Board feet are always figured on nominal size.
How this is worked out
The formula
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
= thickness (in) × width (in) × length (in) ÷ 144
1 board foot = 144 cubic inches = a 1 × 12 board one foot longOpen How it’s calculated above to see this worked through with your own numbers.
What you enter
- Thickness
- Nominal for softwood (a 2×4 is 2). Hardwood in quarters: 4/4 = 1 in, 5/4 = 1.25, 8/4 = 2.in in, mm, cm · 0 or more · defaults to 1
- Width
- Nominal for dimensional lumber; actual measured width for random-width hardwood.in in, mm, cm · 0 or more · defaults to 6
- Length
- A number.in ft, in, m, cm · 0 or more · defaults to 8
- Number of pieces
- A number.from 1 to 100000 · whole numbers only · defaults to 10
- Price per board foot(under More options)
- Hardwood dealers quote per board foot. Leave 0 to skip.in dollars · 0 or more · defaults to 0
What you get back
- Board feetmain answer
- Board feet per piece
- Total linear feet
- Cubic feet of wood
- Board feet ÷ 12.
- Cost
What this assumes
- Board feet are calculated on the dimensions you enter — use nominal sizes for softwood and rough thickness for hardwood, as dealers do.
- No rounding to the nearest board foot per piece; tallies at a yard may round each board.
About this calculator
A board foot is a volume: a piece of wood 1 inch thick, 12 inches wide and 1 foot long — 144 cubic inches. Hardwood is priced by it because boards come in random widths and lengths, so a per-piece or per-foot price would be meaningless. Enter the thickness, width and length of one piece and how many you need, and the calculator gives total board feet and cost.
Nominal versus actual
Softwood dimensional lumber (2×4, 1×6) is named by its rough-sawn size, but after drying and planing a 2×4 is actually 1½ × 3½ in. Board feet are figured on the nominal size — an 8-ft 2×4 is 5.33 board feet, not 3.5. The table below lists actual sizes from the American Softwood Lumber Standard so you can plan joinery, but enter nominal numbers here for pricing.
Hardwood is different: it's sold in the rough, by thickness in quarters of an inch. "4/4" (four-quarter) is 1 in, 5/4 is 1¼, 8/4 is 2 in. If you buy it surfaced (S2S or S4S), it will measure less — 4/4 planed to 13/16 or ¾ — but you still pay for the full quarter thickness it started as. Widths are measured to the nearest inch on the actual board, and anything under an inch thick is billed as 4/4.
Using it at the lumberyard
Yards tally each board as they pull it: thickness × width × length ÷ 12, rounded to the nearest board foot or half. For a project cut list, add up the board feet of each part, then add 15–30% for defects, grain matching, planing and cutoff — more for figured wood or wide panels glued from narrow stock. Enter the total under Number of pieces as 1 with your summed dimensions, or run the calculator per part and add.
Linear feet, square feet and board feet
Molding and trim are sold by the linear foot regardless of size. Plywood and flooring are by the square foot or sheet. Only solid lumber is by the board foot, and only hardwood consistently — construction lumber is priced per piece, though the yard still uses board feet to figure a truckload. If you're converting a per-board-foot price to per-piece, multiply by the board feet per piece shown above.
Frequently asked questions
▸How many board feet are in a 2×4?
An 8-ft 2×4 is 5.33 board feet (2 × 4 × 8 ÷ 12). A 10-footer is 6.67 and a 12-footer is 8. Board feet always use the nominal 2 × 4, not the actual 1½ × 3½.
▸What does 4/4, 5/4 and 8/4 mean?
Hardwood thickness in quarters of an inch, measured rough: 4/4 is 1 in, 5/4 is 1¼ in, 6/4 is 1½ in, 8/4 is 2 in. You pay for the rough thickness even if the board has been planed thinner.
▸How do I convert linear feet to board feet?
Multiply linear feet by the board's thickness and width in inches, then divide by 12. Twenty linear feet of 1×8 is 20 × 1 × 8 ÷ 12 = 13.33 board feet.
▸Why is a 2×4 not 2 inches by 4 inches?
Lumber is named by its rough-sawn size. Drying shrinks it and planing smooths it, leaving 1½ × 3½ in. The sizes are standardized in the American Softwood Lumber Standard, PS 20.
▸How much extra lumber should I buy for a woodworking project?
15–20% over the cut list for straightforward work, 30% or more for wide glue-ups, figured wood or when you need to match grain and color across parts.
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