Board Feet Calculator
Lumber volume in board feet from thickness, width, length, and piece count.
What it does
A board foot is the lumber trade volume unit: a piece one foot square and one inch thick, or 144 cubic inches in any shape. Hardwood dealers price by it because it tracks wood substance better than piece counts across random widths and lengths.
The tool above takes actual thickness and width in inches with length in feet, plus the piece count. It returns volume per board and for the lot, with cost at your per board foot price.
Nominal versus actual sizes trip up beginners. A hardware store 2x8 is named for rough size but planes down to 1.5 by 7.25 inches. Hardwood sold rough or surfaced follows its own conventions, so measure the stack or ask the tally rule before multiplying.
Expect the invoice slightly above the raw total. Yards commonly round each board up to the next quarter or half foot, and surfacing removes wood you still pay for.
How to use
- Measure actual thickness and width with a tape, not the stamped name.
- Enter length in feet and the number of equal pieces.
- Read per board volume first as a sanity check against the yard tally.
- Multiply by price per board foot for the lot estimate.
Formula
- thickness x width
- Cross section in square inches, using actual measured sizes.
- length in feet
- Board length. The 12 below converts inches to feet.
- 12
- Inches per foot. One board foot equals 144 cubic inches.
- pieces
- Count of identical boards. Mixed sizes need separate passes.
For full inches and feet the shortcut reads: a 1 inch thick, 12 inch wide, 1 foot long board is exactly 1 board foot. Everything else scales from there.
Worked example
Example: six boards, 2 x 8 in, 10 ft long
Thickness 2, width 8, length 10, six pieces, $4 per board foot.
- Per board: 2 x 8 x 10 / 12 = 160 / 12 = 13.33 bf.
- Total: 13.33 x 6 = 80 bf.
- Cost: 80 x $4 = $320.00 before tax and surfacing.
- Sanity check: 80 bf is 80 x 144 = 11,520 cubic inches of wood.
Reference table
| Board | Actual inches | Board feet |
|---|---|---|
| 1x6, 8 ft | 0.75 x 5.5 | 2.75 bf |
| 2x4, 8 ft | 1.5 x 3.5 | 3.50 bf |
| 2x8, 8 ft | 1.5 x 7.25 | 7.25 bf |
| 2x10, 10 ft | 1.5 x 9.25 | 11.56 bf |
| 4x4, 8 ft | 3.5 x 3.5 | 8.17 bf |
Limits
- Assumes identical rectangular boards. Tapered or live edge slabs need averaging.
- Uses sizes you enter. Nominal name sizes give wrong answers for 2x stock.
- Ignores waste, defects, and grain matching, which add 10 to 30% on real projects.
- Dealer rounding and surfacing policies sit outside the math.
Common mistakes
- Using the stamped 2x8 size (2 x 8) instead of actual 1.5 x 7.25, which overstates by half.
- Mixing inches and feet without the divide by 12.
- Pricing hardwood by the piece against per board foot quotes.
- Forgetting offcut waste on short cut lists.
- Measuring one board and assuming the bundle matches.
Try it yourself
Quick checks. Answers sit tucked under each question.
One board, 1 in thick, 6 in wide, 8 ft long. Board feet?
1 x 6 x 8 / 12 = 4 bf.
Ten 2x4 studs at actual 1.5 x 3.5 in, 8 ft. Total?
Each is 1.5 x 3.5 x 8 / 12 = 3.5 bf. Ten make 35 bf.
Questions
What is a board foot exactly?
144 cubic inches of lumber: for example 1 in thick, 12 in wide, and 1 ft long.
Why is a 2x4 not 2 by 4 inches?
Names date to rough sawn sizes. Planing and drying shrink a 2x4 to 1.5 by 3.5 inches.
How do yards round board feet?
Most round each board up to an agreed fraction. Ask the tally rule, since it moves the invoice a few percent.
Is plywood sold by board feet?
No. Sheet goods sell by the sheet or square foot. Board feet cover solid lumber.
How much extra should I buy?
Ten percent for straight builds, up to thirty with defects, grain matching, or short stock.
Does length have to be feet?
No, any consistent units work with the right divisor, but inches with feet divided by 12 is the trade standard.