How to use the board foot calculator calculator
- 1
Use the nominal size
The board-foot convention is based on the size lumber is sold as, not its planed dimensions. A board sold as a 2 by 10 is calculated as 2 by 10 even though the finished piece is smaller.
- 2
Enter thickness, width, and length
Thickness and width go in inches; length can be entered in feet or inches using the unit selector.
- 3
Set the quantity
Enter how many identical pieces of that size you need. The board footage scales directly with the count.
- 4
Add other sizes
Use the add button for each additional size in the order. The calculator lists the board feet for each size and totals them.
- 5
Price it if lumber is sold that way
Enter your price per board foot for an estimated total. Hardwood is usually priced this way; framing lumber is more often priced per piece.
Formula
Board feet = (thickness(in) x width(in) x length(ft)) / 12
When the length is in inches instead, divide by 144. Both come from the definition of a board foot as 144 cubic inches.
Worked example
Twelve boards sold as 2 by 10, each 16 feet long
- 1Board feet for one: (2 x 10 x 16) / 12 = 26.67.
- 2Multiply by the quantity: 26.67 x 12 = 320.
The order is 320 board feet.
Worked examples
A single small board
One board sold as 1 by 6, eight feet long
- 1Board feet: (1 x 6 x 8) / 12 = 4.
- 2The arithmetic is exact here, since 6 x 8 divides evenly by 12.
The board is exactly 4 board feet. A 1 inch board is convenient because its board footage equals its square footage.
Mixing sizes in one order
Ten 2 by 4 at 8 feet, plus four 4 by 4 at 8 feet
- 12 by 4 at 8 ft: (2 x 4 x 8) / 12 = 5.33 each, so 53.33 for ten.
- 24 by 4 at 8 ft: (4 x 4 x 8) / 12 = 10.67 each, so 42.67 for four.
- 3Total: 53.33 + 42.67 = 96 board feet.
The order is 96 board feet across two sizes. Adding sizes separately and totaling at the end is how a real lumber list works.
What a board foot actually measures
A board foot is a unit of volume, not of area or length. One board foot is 144 cubic inches, which you can picture as a piece of board one foot square and one inch thick.
That shape is why the formula divides by 12. Thickness and width are in inches while length is in feet, so multiplying them gives inch-inch-feet, and dividing by 12 converts to the 144 cubic inch unit. If you work entirely in inches, divide by 144 instead and you get the same answer.
A useful consequence: for lumber one inch thick, board feet and square feet are the same number. A 1 by 6 at 8 feet is 4 square feet of surface and 4 board feet of volume. That equivalence breaks as soon as the thickness changes.
Nominal size versus actual size
Softwood lumber is sold by a nominal size that is larger than the piece you actually receive. A board sold as a 2 by 4 measures less than that once it has been surfaced, because the nominal figure describes it before drying and planing.
The board-foot convention uses the nominal size. That may look like overcharging, but it reflects that the mill did cut and handle a piece of that rough size, and it keeps pricing consistent across suppliers who surface to slightly different finished dimensions.
So enter the size the lumber is sold as. Entering measured finished dimensions will give a smaller number than the yard will bill you for, which is exactly the wrong direction for a budget.
How hardwood thickness is described
Hardwood is often described in quarters of an inch rather than in whole inches. A board described as four-quarter is one inch thick, six-quarter is one and a half, and eight-quarter is two.
That system exists because hardwood is sold rough and in a wider range of thicknesses than softwood framing stock. Once you know the convention, converting is simple: divide the quarter figure by four to get inches, and enter that.
Hardwood is also usually sold in random widths and lengths rather than in fixed dimensions, which is another reason it is priced by board foot rather than by the piece. You are buying a volume of material, not a set of identical parts.
Common mistakes
Where board-foot calculations go wrong:
- Using measured finished dimensions instead of the nominal size the lumber is sold as.
- Dividing by 144 when the length is in feet, or by 12 when it is in inches.
- Confusing board feet with linear feet when ordering.
- Forgetting to multiply by the number of pieces.
- Reading a hardwood quarter thickness as inches, so treating eight-quarter as eight inches instead of two.
- Assuming board feet and square feet are interchangeable, which is only true at one inch thick.
Sources and methodology
Every figure on this page comes from geometry rather than from a product database. Areas use the standard area formulas, counts divide an area by the size of one unit, and unit conversions use exact factors: 12 inches to a foot, 9 square feet to a square yard, and 100 square feet to a roofing square.
YardCalc publishes no product dimensions, coverage rates, or prices. Unit sizes differ between manufacturers and regions, and a figure that is right for one product is wrong for another, so the calculator asks you for the size of the product you are actually buying. Prices are yours alone.
Results are planning estimates, not order quantities. Read how every value on the site is derived and checked in the YardCalc calculation methodology.
Board feet per piece by nominal size and length
Board feet in one piece at each nominal size and length, from thickness times width times length divided by 12.
| Nominal size | 8 ft | 10 ft | 12 ft | 14 ft | 16 ft |
|---|---|---|---|---|---|
| 1 x 4 | 2.67 | 3.33 | 4 | 4.67 | 5.33 |
| 1 x 6 | 4 | 5 | 6 | 7 | 8 |
| 1 x 8 | 5.33 | 6.67 | 8 | 9.33 | 10.67 |
| 2 x 4 | 5.33 | 6.67 | 8 | 9.33 | 10.67 |
| 2 x 6 | 8 | 10 | 12 | 14 | 16 |
| 2 x 8 | 10.67 | 13.33 | 16 | 18.67 | 21.33 |
| 2 x 10 | 13.33 | 16.67 | 20 | 23.33 | 26.67 |
| 2 x 12 | 16 | 20 | 24 | 28 | 32 |
| 4 x 4 | 10.67 | 13.33 | 16 | 18.67 | 21.33 |
Frequently asked questions
- How do you calculate board feet?
- Multiply thickness in inches by width in inches by length in feet, then divide by 12. A 2 by 10 at 16 feet is (2 x 10 x 16) / 12, which is 26.67 board feet.
- What is a board foot?
- A unit of volume equal to 144 cubic inches: a piece of board one foot square and one inch thick. It is how rough and hardwood lumber is normally priced.
- Do I use nominal or actual lumber size?
- Nominal, meaning the size the lumber is sold as. A board sold as a 2 by 4 is calculated as 2 by 4 even though the surfaced piece measures less. Using the finished dimensions gives a lower figure than the yard will bill.
- What does four-quarter or eight-quarter mean?
- Hardwood thickness expressed in quarters of an inch. Four-quarter is one inch, six-quarter is one and a half, and eight-quarter is two inches. Divide the quarter figure by four to get inches.
- Is a board foot the same as a square foot?
- Only for lumber exactly one inch thick. A board foot is a volume and a square foot is an area, so they diverge as soon as thickness changes. A 2 inch board has twice the board footage of a 1 inch board of the same face size.
- Is a board foot the same as a linear foot?
- No. A linear foot is a foot of length whatever the board size, which is how trim is usually sold. A board foot accounts for thickness and width as well.
Board feet come from the exact definition of 144 cubic inches, using the nominal dimensions you enter. No lumber size, grade, or price is assumed. Counts come from exact geometry using the product dimensions you enter. Confirm the product size, the layout, cutting and breakage, and the final order quantity with your supplier before purchasing.
Results are planning estimates. Last reviewed 2026-08-30.