What this calculator does
A board foot is a volume unit: 144 cubic inches, equivalent to a piece one foot square and one inch thick. Ten pieces of 1 by 6 inch lumber, eight feet long, come to 40 board feet.
It is a volume rather than an area, which is the thing to get straight. Doubling the thickness doubles the board feet even though the boards cover the same area, so a 2 by 6 costs twice what a 1 by 6 of the same length does. Hardwood is priced this way precisely because it is sold in varying thicknesses.
The formula
Board feet are the length in feet multiplied by the width and thickness in inches, divided by twelve. The quantity multiplies that for the batch. Note that hardwood is normally priced on nominal or rough-sawn dimensions before surfacing, so a board sold as one inch thick may measure three quarters once dressed.
| Term | Meaning |
|---|---|
| Board foot | 144 cubic inches of lumber: 12 × 12 × 1 inches. |
| Nominal dimension | The size a board is sold as, before surfacing. A 2×4 actually measures 1.5 × 3.5 inches. |
| Quarter measure | Hardwood thickness in quarter inches: 4/4 is one inch, 8/4 is two. |
| Surfaced | Planed smooth, which removes material from the rough dimensions. |
The inputs explained
| Field | What to enter |
|---|---|
| Thickness (in) | Thickness in inches, usually the nominal or rough dimension. |
| Width (in) | Width in inches. |
| Length (ft) | Length in feet. |
| Number of pieces | Number of pieces. |
| Price per board foot ($) | Price per board foot, for the cost estimate. |
When to use it
Buying hardwood
Hardwood is priced by the board foot rather than by the piece, so the volume is what determines the cost.
Estimating a project
Converting a cutting list into board feet gives a material cost before buying.
Comparing prices
Lumber quoted per piece and per board foot is not comparable until both are on the same basis.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How does thickness affect the cost?
The same boards at a range of thicknesses.
| Thickness | Total board feet | Board feet per piece | Estimated cost |
|---|---|---|---|
| 1 in | 40.00 | 4.000 | $180.00 |
| 2 in | 80.00 | 8.000 | $360.00 |
| 4 in | 160.00 | 16.000 | $720.00 |
Questions
What is a board foot?
A volume of 144 cubic inches, equal to a board one foot square and one inch thick. It is the standard unit for pricing hardwood in North America, because hardwood is sold in varying thicknesses and widths rather than in fixed dimensional sizes.
Do I use nominal or actual dimensions?
Nominal, usually, since that is what suppliers price against. A board sold as 1 inch thick may measure three quarters once surfaced, but you pay for the inch. Check with the supplier, since practice varies and rough-sawn stock is measured as it is.
What does 4/4 mean?
Four quarters of an inch, so one inch thick. Hardwood thickness is conventionally expressed in quarters: 4/4 is one inch, 6/4 is one and a half, 8/4 is two. It is read aloud as four-quarter rather than four over four.
Is a board foot the same as a linear foot?
No. A linear foot is just length, ignoring the cross-section entirely. A board foot is a volume. Ten linear feet of 1×6 is 5 board feet, while ten linear feet of 2×12 is 20, despite both being ten feet of timber.
For lumber weight, see the lumber weight calculator. For framing quantities, see the wall stud calculator.