Board Foot Calculator
Board feet use the sizes you enter: nominal for softwood (a 2x4 counts as 2 × 4), rough thickness for hardwood (4/4 counts as 1 in). The starting price is an example. Weight is an average at about 12% moisture; wet lumber weighs more.
A board foot is 144 cubic inches, the volume of a board 1 in thick, 12 in wide, and 1 ft long. For each board, multiply thickness (in) × width (in) × length (ft) and divide by 12. An 8 ft 2x4 is 5.33 board feet. Six 1×6×8 boards and four 2×4×8s total 45.33 board feet, or 52.13 with 15% waste. At an example $6 per board foot, that costs $312.80. Add one row per board size below.
Board feet in common lumber sizes
| Lumber | Board feet each | Pieces per 100 board feet |
|---|---|---|
| 1×4, 8 ft | 2.67 | 37.5 |
| 1×6, 8 ft | 4 | 25 |
| 1×8, 8 ft | 5.33 | 18.8 |
| 1×12, 8 ft | 8 | 12.5 |
| 2×4, 8 ft | 5.33 | 18.8 |
| 2×6, 8 ft | 8 | 12.5 |
| 2×8, 10 ft | 13.33 | 7.5 |
| 2×10, 12 ft | 20 | 5 |
| 2×12, 16 ft | 32 | 3.1 |
| 4×4, 8 ft | 10.67 | 9.4 |
| 6×6, 8 ft | 24 | 4.2 |
How to calculate board feet
One board foot is 12 in × 12 in × 1 in, or 144 cubic inches. There are three equivalent ways to get there:
- Inches and feet: thickness (in) × width (in) × length (ft) ÷ 12. This is the usual one, because lumber lengths are in feet.
- All inches: thickness × width × length ÷ 144. Use it for short parts on a cut list. Switch the Units picker to "Inches (all three)."
- Pieces: multiply one board by the number of boards of that size.
A 2x4 that's 8 ft long is 2 × 4 × 8 ÷ 12 = 5.33 board feet. A 1×6 that's 8 ft long is 4 board feet. Six of the 1×6s make 24 and four of the 2x4s make 21.33, for 45.33 in total.
Nominal, actual, and rough sizes
Board feet are counted on the size the lumber is sold by, which is not always what you measure:
- Softwood dimensional lumber: a 2x4 measures about 1.5 × 3.5 in, but board feet use the nominal 2 × 4. Enter 2 and 4.
- Hardwood: sold by thickness in quarters of an inch. 4/4 is 1 in, 5/4 is 1¼ in, 6/4 is 1½ in, and 8/4 is 2 in. McIlvain, a hardwood lumber dealer, says board feet use that rough thickness even when you buy the board surfaced. A surfaced 4/4 board is about 13/16 in thick, and using that figure undercounts by about 19%. Wikipedia instead says hardwood uses actual measurements, so ask your yard which way it tallies.
- Random widths: hardwood often comes in mixed widths and lengths. Measure each board, or add a row per width.
How much extra lumber to buy
There is no standard figure. The presets follow what woodworkers report:
- 15%: surfaced (S4S) boards and simple cuts. One contributor on WoodWeb notes that with S3S or S4S stock, part of the waste is already in the price.
- 30%: rough lumber. A shutter maker in the same thread allows 10% for cutting, 10% for processing, and 10% for defects and damage.
- 50%: rough lumber milled to a finished size. The same thread gives 25% lost going from 1 in green to 3/4 in finished, plus 5 to 15% for straight-line and end cuts.
Add more for color or grain matching, and less if you pick each board yourself.
Lumber cost and weight
Hardwood is priced per board foot, so cost is board feet with waste × price. The $6 starting price is only an example, so use your yard's price. Softwood at a home center is usually priced per piece. To compare it, divide the piece price by its board feet: a $5 2x4x8 is $0.94 per board foot.
Weight is the ordered volume times the species' average dried weight, from The Wood Database. In the example, 52.13 board feet of red oak is 0.123 m³ and weighs about 190 lb. That matters for a car roof or a truck bed. Green or wet lumber is much heavier.
Common mistakes
- Dividing by 144 with the length in feet. Use 12 when the length is in feet and 144 when all three are in inches.
- Using the planed thickness for hardwood. Most dealers tally 4/4 as 1 in, so check how yours counts.
- Forgetting the waste. Ends get trimmed, defects get cut out, and rough boards lose thickness when you plane them.
- Confusing board feet with linear feet. A linear foot is only a length. The calculator shows both, so you can check a quote either way.
The examples and table figures were checked with this calculator.
Frequently asked questions
How do you calculate board feet?
Multiply thickness (in) × width (in) × length (ft) and divide by 12. A 1 × 6 board that is 8 ft long is 1 × 6 × 8 ÷ 12 = 4 board feet. If all three are in inches, divide by 144 instead.
How many board feet are in a 2x4x8?
5.33 board feet. Board feet for softwood lumber use the nominal size, 2 × 4 in, even though the board measures about 1.5 × 3.5 in.
What is a board foot?
A board foot is 144 cubic inches: a board 1 in thick, 12 in wide, and 12 in long. It is about 0.00236 cubic meters, and 12 board feet make a cubic foot.
How do I calculate board feet for 4/4 or 8/4 lumber?
Use the quarter count as the thickness in inches: 4/4 is 1 in, 5/4 is 1.25, 8/4 is 2. An 8/4 board 8 in wide and 8 ft long is 2 × 8 × 8 ÷ 12 = 10.67 board feet.
How much extra lumber should I buy?
About 15% for surfaced boards and simple cuts, 30% for rough lumber, and up to 50% if you mill rough stock down to a finished size. Add more if you need grain or color to match.
How many board feet are in a cubic foot?
Twelve. A cubic foot is 1,728 cubic inches, and a board foot is 144. A cubic meter is about 424 board feet.
What is the difference between a board foot and a linear foot?
A linear foot is a length, whatever the board size. A board foot is a volume. An 8 ft 2x4 is 8 linear feet and 5.33 board feet.
How much does lumber weigh?
It depends on the species and moisture. Dried red oak averages about 44 lb per cubic foot, or 3.7 lb per board foot. Eastern white pine is about 25 lb per cubic foot.
Related calculators
Sources
- Board footWikipediaDefinition as 144 in³ (about 0.00236 m³); surfaced softwood is counted on nominal dimensions.
- The Board Foot: Definition and FormulaMcIlvain HardwoodsQuarter thicknesses (4/4 = 1 in rough, 13/16 in surfaced); hardwood board feet use rough thickness.
- Calculating Waste from Rough LumberWoodWebWoodworkers’ waste allowances for rough lumber, from 10% cutting waste up to about 50% from rough to finished.
- Wood species pages (Average Dried Weight)The Wood DatabaseAverage dried weights used for the species list, e.g. red oak 700 kg/m³ (43.8 lb/ft³), eastern white pine 400 kg/m³.