Board Foot Calculator
This board foot calculator finds how many board feet are in a piece of lumber from its thickness, width, and length. Enter the board size and quantity to get total board feet, and add a price per board foot for an instant lumber cost.
Quick answer
A board foot is 144 cubic inches of wood, the same as a board 1 inch thick by 12 inches wide by 12 inches long.
What this tells you
- •A board foot is 144 cubic inches of wood, the same as a board 1 inch thick by 12 inches wide by 12 inches long.
- •With length in feet, board feet equal thickness times width times length, divided by 12.
- •Board feet use the nominal size you are charged for, not always the finished dimensions.
- •Use the dimensions on the supplier's tally because rough, surfaced, and construction lumber may be measured differently.
- •Add waste separately for defects, end checks, grain selection, milling, and cutting losses.
How to Use
- 1Enter board thickness and width in inches.
- 2Enter board length in feet.
- 3Set the quantity of identical boards.
- 4Optionally enter your price per board foot.
- 5Calculate for total board feet and cost.
How It Works
Formula
Board Feet (one board) = Thickness(in) x Width(in) x Length(ft) / 12
Total Board Feet = Board Feet x Quantity
Cost = Total Board Feet x Price per Board FootBecause a board foot equals 144 cubic inches and a foot of length is 12 inches, the calculation reduces to thickness times width in inches times length in feet, divided by 12.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
How many board feet in a 2x6x8?
Twelve 1x8x10 boards at $4.50 per bf
Board Feet for Common Lumber Sizes
Board feet per piece for standard nominal sizes at an 8-foot length.
| Nominal Size | Length | Board Feet |
|---|---|---|
| 1x4 | 8 ft | 2.67 |
| 1x6 | 8 ft | 4.00 |
| 1x12 | 8 ft | 8.00 |
| 2x4 | 8 ft | 5.33 |
| 2x6 | 8 ft | 8.00 |
| 2x8 | 8 ft | 10.67 |
| 4x4 | 8 ft | 10.67 |
Multiply by the number of boards for a total. A 2x6x8 is 8 board feet.
What Is a Board Foot?
A board foot is the standard unit for buying and pricing rough lumber, especially hardwood. One board foot is 144 cubic inches, which you can picture as a board 1 inch thick, 12 inches wide, and 12 inches long. It measures volume, so a thicker or wider board holds more board feet per running foot.
Hardwood thickness is often quoted in quarters, where 4/4 means 1 inch and 8/4 means 2 inches. Softwood from the home center is usually sold by the piece at nominal sizes, but the board foot is still how you compare value across thicknesses and species.
Nominal and actual dimensions answer different questions. A construction 2x6 is commonly about 1.5 by 5.5 inches after drying and dressing, but a store may sell it by the piece rather than by calculated board feet. Hardwood dealers often tally rough stock using its stated rough thickness and measured width and length. Some sellers round widths, lengths, or board-foot totals according to their own rules.
For random-width hardwood, calculate each board from the thickness, measured width, and length used on the invoice, then add the pieces. Entering one average width and a quantity is only accurate when the boards truly share that width and length. Compare the calculator total with the yard's tally before using it to challenge a quote.
A purchase quantity needs more wood than the finished parts alone. Crosscuts remove kerf, jointing and planing reduce dimensions, and boards may contain knots, checks, sapwood, twist, or grain that does not suit a visible part. A cutting plan gives a better waste allowance than one universal percentage. Projects that need matching color or long clear pieces usually need more selection room.
Price per board foot may not be the whole invoice. A supplier can add surfacing, straight-line ripping, milling, delivery, minimum-order charges, taxes, or premiums for wide and long stock. Enter the quoted base rate here for a material subtotal, then add those charges separately. Confirm whether the listed price applies to the species, grade, thickness, and quantity you need.
Board feet measure volume, not coverage or structural capacity. Flooring coverage depends on finished face width and installation waste. Decking, framing, and sheet goods are often estimated by pieces, linear feet, square feet, or sheets. Structural lumber selection also depends on species, grade, span, loading, moisture, and local requirements, none of which this volume calculation checks.
Common mistakes
- Entering length in inches instead of feet
- Confusing board feet with linear feet
- Using finished dimensions when you are charged for the nominal size
- Forgetting to set the quantity for multiple boards
- Assuming every supplier tallies nominal and dressed stock in the same way
- Using board feet as square-foot coverage without accounting for finished thickness and width
- Ordering the exact finished-part volume with no allowance for kerf, defects, or milling
- Comparing prices without checking species, grade, thickness, width premiums, and service charges
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