Board Foot Calculator
Convert lumber dimensions into board feet and see what the board costs at your supplier's price per board foot.
Board foot calculator
4.00 board feet per board
Quick conversion for common thicknesses
| Nominal size | Thickness (in) | Board feet per sq ft |
|---|---|---|
| 4/4 | 1.00 | 1.00 |
| 5/4 | 1.25 | 1.25 |
| 6/4 | 1.50 | 1.50 |
| 8/4 | 2.00 | 2.00 |
| 12/4 | 3.00 | 3.00 |
One square foot of 1-inch-thick stock equals one board foot, which is why the numbers line up so neatly.
What a board foot is
A board foot is a volume, not a length. It is 144 cubic inches — the amount of wood in a board 12 inches wide, 12 inches long, and 1 inch thick. Hardwood lumber in the United States is priced and sold by this unit because thickness varies so much between boards.
Softwood construction lumber works differently. A 2 × 4 is sold by the piece or by linear foot, and its "2 × 4" label is nominal: the actual surfaced size is 1½ inches by 3½ inches.
The formula
With all dimensions in inches: board feet = thickness × width × length ÷ 144. With length in feet, which is how lumber is usually measured: board feet = thickness × width × length (ft) ÷ 12.
Why nominal thickness matters
Hardwood is priced before it is planed. A 4/4 board starts at 1 inch thick and ends up around 13/16 inch after surfacing, but you still pay for the full inch. If you measure the finished board and use that number, you will underestimate the cost of your order.
Width is treated the same way: a board that is 5¾ inches wide is usually sold as 6 inches. Suppliers vary, so ask whether they round up to the next inch — many do.
Estimating a project
- List every part you need to cut, with finished dimensions.
- Add allowance for waste: 15% for simple projects, 25% or more when matching grain or bookmatching.
- Convert each part to board feet with the formula above.
- Group by thickness, then compare the total with your supplier's price per board foot.
A common mistake is pricing a project by the square foot of finished surface. That ignores thickness, so 8/4 stock ends up costing twice what you budgeted.
Nominal vs. actual sizes
Construction lumber is named by its rough size, then planed down. Board feet are calculated from the nominal dimensions, which is why a “2 × 4” prices as 2 × 4 even though it measures 1½ × 3½ inches.
| Nominal | Actual (surfaced) | Board feet per 8 ft |
|---|---|---|
| 1 × 4 | ¾ × 3½ in | 2.67 |
| 1 × 6 | ¾ × 5½ in | 4.00 |
| 2 × 4 | 1½ × 3½ in | 5.33 |
| 2 × 6 | 1½ × 5½ in | 8.00 |
| 2 × 8 | 1½ × 7¼ in | 10.67 |
| 4 × 4 | 3½ × 3½ in | 10.67 |
Hardwood weight and price ranges
Freight and shelving capacity depend on weight, not just board feet. Rough averages at 8% moisture content:
| Species | Weight (lb per BF) | Typical rough price ($/BF) |
|---|---|---|
| Red oak | 3.7 | $4–8 |
| Hard maple | 3.6 | $5–9 |
| Black walnut | 3.1 | $8–15 |
| Cherry | 2.9 | $6–12 |
| Poplar | 2.6 | $3–6 |
| Eastern white pine | 2.4 | $3–6 |
Prices vary by region, grade, and thickness; 8/4 stock usually costs more per board foot than 4/4 of the same species.
Board feet, linear feet, and square feet answer three different questions
Most pricing arguments at a lumber yard come from mixing these up, and each has a legitimate use.
- Linear feet is what a project consumes when the part is a length: trim, a rail, a fascia board. You are buying a stick of a given length regardless of how wide it is.
- Square feet is what a surface consumes: a panel, a floor, a table top. Here width matters and thickness usually does not.
- Board feet is what the mill bills. It is the only unit that accounts for thickness, which is why it is the only one that works across a mixed order of 4/4 and 8/4 stock.
The conversion you will actually use: board feet per linear foot is the nominal width divided by 12. A 1 × 6 is 0.5, so at $5 per board foot it costs $2.50 a linear foot. Multiply that by the number of feet you need and you have a number you can compare against a big-box price per piece without doing arithmetic in the aisle.
What the total does not include
Board footage prices the wood. It does not price planing, ripping to width, jointing an edge, or delivery, and those are separate line items at most yards. It also does not price the waste between the parts, which is the number that decides whether a project comes in on budget.
Two rules keep this honest. Add 15 percent for a straightforward project built from rectangular parts. Add 30 percent when grain has to match across a glue-up, because matching is a selection problem: you reject boards that are the right size and the wrong colour, and rejected boards are already paid for.
Frequently asked questions
How do you calculate board feet?
Thickness (in) × width (in) × length (in) ÷ 144, or thickness × width × length in feet ÷ 12. A 1 × 6 × 8 ft board is 4 board feet.
Board foot vs. linear foot — what is the difference?
A linear foot measures length only. A board foot measures volume, so it accounts for thickness and width. Hardwood is sold by the board foot; trim and framing are sold by the linear foot.
Do I use nominal or actual thickness?
Nominal, for pricing. A 4/4 board is billed as 1 inch thick even though it measures about 13/16 inch after planing.
How many board feet is a 2 × 4 × 8?
2 × 4 × 8 ÷ 12 = 5.33 board feet using nominal dimensions. Construction lumber is normally sold by the piece, so this is mainly useful for comparing volume.
How much waste should I add?
15% for straightforward furniture and shelving, 25% when you need matched grain, wide boards, or complex joinery. Buying an extra board is cheaper than a second trip to the lumber yard.
Disclaimer: This calculator provides estimates only. Suppliers differ in how they round thickness and width, and prices exclude tax, delivery, and milling charges. Confirm quantities and pricing with your lumber yard before ordering.
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