How to use
- Choose the thickness and width that apply to your lumber tally, in inches or centimeters.
- Enter board length in feet or meters, then the number of identical boards.
- Leave the rate blank for volume alone, or enter your own quote per board foot.
- For mixed dimensions, calculate each group and combine the board-foot totals.
How the estimate is calculated
Board feet = thickness in inches × width in inches × length in feet ÷ 12 × quantity. This is equivalent to dividing cubic inches by 144. Divide board feet by 12 for cubic feet; multiply board feet by 144 × 0.0254³ for cubic meters. An optional quote total multiplies board feet by your entered rate.
Example: ten boards measured as 2 in × 6 in × 8 ft contain 2 × 6 × 8 ÷ 12 × 10 = 80.00 board feet. Their combined volume is 6.7 cu ft, or 0.19 m³. The dimensions in this example are the tally dimensions, not a claim about the actual size of a nominal retail board.
Quarter names expressed as thickness
| Quarter notation | Thickness before any surfacing allowance | Basis |
|---|---|---|
| 4/4 | 1 in | 4 ÷ 4 |
| 5/4 | 1.25 in | 5 ÷ 4 |
| 6/4 | 1.5 in | 6 ÷ 4 |
| 8/4 | 2 in | 8 ÷ 4 |
| One board foot | 144 cu in | 1 in × 12 in × 12 in |
These are commonly used lumber-planning conventions, not a quotation from a grading rule. Ask the seller whether the tally uses rough, nominal, or surfaced dimensions before comparing an invoice with a measurement.
Rough stock and surfaced boards
A rough board may be sold using its rough tally even after surfacing removes material. A tape measurement of the finished board can therefore produce a different geometric volume. Use one consistent basis when comparing two quotes; do not silently mix a rough thickness with a surfaced width unless that is the seller’s stated method.
Board-foot volume also does not describe usable yield. Knots, checks, grain direction, and your cut list affect how much of the board reaches the finished project. Plan those cuts separately; quantity here simply multiplies identical boards and adds no automatic waste.
Common mistakes
- Do not enter width in feet in the US width field; it expects inches.
- Linear feet describe length only. They cannot replace board feet without thickness and width.
- Do not assume a quarter name guarantees the final surfaced thickness. Confirm the stock specification.
Sources
Formula and quarter notation: commonly used lumber-planning conventions; confirm the seller’s tally basis. Metric conversion follows the exact inch definition of 2.54 centimeters per inch.
Related calculators
- Square Footage Calculator — surface area rather than volume
- Stair Calculator — preliminary flight geometry
Frequently asked questions
Is a board foot the same as a square foot?
No. A square foot is area. A board foot is volume equal to a square foot at one inch thick, using the tally dimensions.
Can I calculate boards with different lengths?
Calculate each size group separately. The quantity box assumes every board in the group has the same dimensions.
What does the optional rate mean?
It is your own quoted amount per board foot, in your chosen currency. The resulting total uses that same currency and adds nothing else.
Does surfacing change the tally?
It can change measured volume, but the seller may use a rough or nominal tally. Confirm their method rather than assuming the finished tape measurement is the billing basis.