Board Foot Calculator
When you shop for hardwood lumber you pay by the board foot. Our calculator removes the guesswork, so you can plan your cut list, estimate volume precisely, and forecast cost with confidence. On this page you’ll learn what a board foot is, how to calculate it step by step, and how to avoid common mistakes when switching between imperial and metric units.
What is a board foot
A board foot (BF) is a volume measure used for hardwood lumber. One board foot equals the volume of a board that’s 1 foot long, 1 foot wide, and 1 inch thick, which is 144 cubic inches. That standard definition is used across the hardwood industry.
You’ll also see abbreviations like BF, BDFT, and FBM in catalogs or price lists. If a supplier quotes “$7.25 per BF,” they mean the price per board foot for that species and grade.
Board foot formula
The simplest way to compute board feet is to keep thickness and width in inches and keep length in feet. Then divide by 12.
BF = (Thicknessin × Widthin × Lengthft) ÷ 12BF = (Tin × Win × Lin) ÷ 144These formulas are recognized by trade groups and lumber suppliers worldwide, and they lead to the same result. Choose whichever fits your measurements.
How to use the calculator
- Enter the number of pieces if you need more than one identical board.
- Type thickness and width. Pick inches, millimeters, centimeters, or meters.
- Enter length. Use a single value with units, or switch to paired inputs such as feet and inches or meters and centimeters.
- Read the board feet per piece and the total board feet instantly.
- Optionally add a price per board foot to see the total cost in your chosen currency.
The calculator handles the unit conversions for you and follows the industry formula shown above.
Units and conversions
Lumber yards describe thickness and width in inches most of the time. Metric projects are straightforward though, because inches and feet convert cleanly to centimeters and meters.
| Quantity | Preferred unit(s) | Helpful conversions |
|---|---|---|
| Thickness | in, mm, cm, m | 1 in = 25.4 mm, 1 in ≈ 2.54 cm |
| Width | in, mm, cm, m | Same as thickness conversions |
| Length | ft, in, m, cm, ft/in, m/cm | 1 ft = 12 in, 1 m ≈ 3.28084 ft |
| Board foot | BF | 1 BF = 144 in³ = 1/12 ft³ |
Worked examples
Example 1: One board
You’re buying a single board that’s 2 in thick, 8 in wide, and 10 ft long. Board feet per piece = (2 × 8 × 10) ÷ 12 = 13.33 BF.
Example 2: Multiple pieces
You need five boards, each 3 in thick and 5 in wide. The length is 7 ft 5 in. Treat 7′ 5″ as 7.4167 feet. Per piece BF = (3 × 5 × 7.4167) ÷ 12 ≈ 9.27. Total BF = 5 × 9.27 ≈ 46.35 BF.
Example 3: Metric plan
Your board is 40 mm thick, 150 mm wide, and 2.4 m long. Convert to inches and feet. Thickness = 40 mm ≈ 1.574 in. Width = 150 mm ≈ 5.906 in. Length = 2.4 m ≈ 7.874 ft. BF ≈ (1.574 × 5.906 × 7.874) ÷ 12 ≈ 6.11 BF.
Board foot vs linear foot vs square foot
- Board foot measures volume. Use it when buying hardwood lumber.
- Linear foot measures length. It ignores thickness and width.
- Square foot measures area. It ignores thickness.
Confusing these units causes busted budgets and short orders. If a supplier lists a price per board foot, always convert your pieces using the board foot formula before multiplying by the price.
Understanding 4/4, 6/4, 8/4 thickness
Hardwood thickness is often expressed in “quarters.” It’s a traditional way to describe rough-sawn thickness in quarter-inch increments. For example, 4/4 means roughly 1 inch thick. 8/4 means roughly 2 inches thick.
| Quarters notation | Nominal rough thickness (in) | Nominal rough thickness (mm) |
|---|---|---|
| 4/4 | 1.00 | 25.4 |
| 5/4 | 1.25 | 31.8 |
| 6/4 | 1.50 | 38.1 |
| 8/4 | 2.00 | 50.8 |
| 10/4 | 2.50 | 63.5 |
| 12/4 | 3.00 | 76.2 |
Retailers price hardwood by the board foot, so a thicker board with the same width and length costs more because the volume increases with thickness.
Estimating project cost
Costs are straightforward once you know total board feet. Multiply total BF by the supplier’s price per BF in your preferred currency. Many price lists clearly state that pricing model.
- Compute total BF with the calculator.
- Ask your supplier for the price per BF for the species and grade.
- Multiply price × total BF to get an estimate.
Real quotes can still move due to grade, width sorting, or surfacing. The calculator shows the volume you’ll pay for, then you can refine species, grade, and milling options with your supplier.
Planning tips to reduce waste
Offcuts happen. Kerf, knots, end checks, and grain matching eat material and time. The right strategy keeps waste under control and keeps your project on schedule.
- Start with a cut list. Plan parts from longest to shortest, then from widest to narrowest.
- Mill in stages. Joint and plane oversized, let boards rest, then sneak up on final size.
- Account for defects. Lower grades mean more culling and more board feet purchased.
- Include a discretionary margin. Published advice varies. Some sources suggest starting near 10–20 percent and adjusting for species, grade, and project complexity. Use the method that fits your risk tolerance, then add that percentage to total BF.
The safest approach is to choose a waste percentage that matches your project and your experience, then apply it transparently on top of the calculator’s board-foot result.
Frequently asked questions
Is board foot an imperial or metric unit
Board foot is an imperial volume unit. It ties back to 144 cubic inches or one-twelfth of a cubic foot. Metric projects can still use it for purchasing because suppliers price by BF even when your plans are metric.
Why does the formula divide by 12
When thickness and width are in inches and length is in feet, multiplying gives in×in×ft. Dividing by 12 converts the length part from feet to inches, which matches the 144 in³ definition.
Can I use all inches instead
Yes. Multiply thickness × width × length, all in inches, then divide by 144. The result equals the feet-based method.
Does surfaced lumber change the board-foot total
Board feet are based on nominal rough thickness. Surfacing reduces actual thickness, yet pricing is still based on the nominal size unless the yard specifies otherwise, so confirm with your supplier.
What about log scales like Doyle or International 1/4-inch
Log rules estimate the potential board feet of a log before sawing. They are separate from the simple board rule used for individual boards.
Quick glossary
- BF (board foot): Volume equal to 1″ × 12″ × 12″.
- FBM or MBF: Thousand board feet.
- FAS, Select, Common: Hardwood grades that influence price and yield.
- Kerf: Material removed by the saw blade.
- Quarters (e.g., 4/4, 8/4): Rough thickness notation in quarter-inch steps.
Further reading: American Hardwood Export Council — Board Foot measurement, Ohio State University — Measuring Standing Trees (board foot definition), Hardwood Store — Board foot formulas.
