Online Tool Store
· 4 min read
How to Calculate Board Feet of Lumber Correctly
Heshan Fernando
Co-founder & COO
You’re at the lumberyard, or pricing out a project’s material list, and the hardwood is priced per board foot — a unit that isn’t the same as a linear foot, and isn’t immediately obvious how to convert to given a board’s actual thickness, width, and length. Get the calculation wrong and you either underestimate your material budget or show up short on lumber for a project.
Board feet is a volume-based unit, not a length-based one, which is exactly what trips people up coming from projects measured in simpler linear terms — a thicker or wider board of the same length contains more board feet, and the formula needs all three dimensions, not just length.
What calculating board feet actually involves
One board foot is a volume of wood equal to a board one inch thick, twelve inches wide, and twelve inches long — or any combination of thickness, width, and length that multiplies to that same volume. The formula is thickness (inches) times width (inches) times length (inches), divided by 144, giving board feet for a single board — then multiplied by quantity for a full order of multiple boards of the same dimensions.
Why people get stuck here
- Confusing board feet with linear feet. Linear feet only measures length; board feet accounts for the full volume, so two boards of the same length but different thickness or width contain meaningfully different board footage.
- Mixing up nominal and actual lumber dimensions. A board sold as “1x6” often has actual finished dimensions slightly smaller than the nominal size, and pricing calculations should generally use nominal dimensions consistent with how the lumberyard prices it, unless told otherwise.
- Forgetting to multiply by quantity for a multi-board order. Calculating board feet correctly for one board and then forgetting to scale up for however many identical boards you need leads to a significant under-order.
- Not double-checking against the lumberyard’s own pricing convention. Some yards round board footage per piece before pricing, which can create small discrepancies from a pure calculated total — worth confirming ahead of a larger order.
What a good board feet calculator looks like
Computes from thickness, width, and length together
Taking all three dimensions into account, rather than just length, gives an accurate board foot figure that matches how lumber is actually priced.
Multiplies by quantity for a full order
Scaling the per-board calculation up to a full order of multiple identical boards removes a common source of under-ordering error.
Includes a total cost estimate at a given price per board foot
Converting the board foot total directly into an estimated dollar cost, given a price per board foot, turns the calculation into an immediately usable budget figure.
| Board Size | Board Feet (per linear foot) | Board Feet (8 ft length) |
|---|---|---|
| 1x4 | 0.33 | 2.67 |
| 1x6 | 0.5 | 4.0 |
| 2x6 | 1.0 | 8.0 |
| 2x8 | 1.33 | 10.67 |
Common mistakes to avoid
- Treating board feet as equivalent to linear feet, which understates or overstates the actual material volume depending on the board’s thickness and width.
- Using actual (finished) dimensions instead of nominal dimensions when the lumberyard prices based on nominal size, or vice versa — always match the yard’s own convention.
- Forgetting to multiply the per-board calculation by the total quantity needed for the project.
- Not accounting for waste factor (cutoffs, defects, mistakes) when ordering exactly the calculated board footage with no buffer.
- Assuming all species and grades of lumber are priced identically per board foot — prices vary significantly by wood type and quality grade.
How to do it with Board Feet Calculator
Online Tool Store’s Board Feet Calculator computes your total entirely in your browser.
- Open the Board Feet Calculator tool.
- Enter a board’s thickness, width, and length, plus the quantity needed.
- Get the total board feet for your order.
- Enter a price per board foot to get an estimated total material cost.
Frequently asked questions
What’s the difference between board feet and linear feet?
Linear feet measures only length, ignoring thickness and width entirely. Board feet is a volume measurement that accounts for all three dimensions, which is why it’s the standard unit for pricing hardwood lumber — two boards of identical length but different thickness contain different amounts of actual wood.
Should I use nominal or actual lumber dimensions?
It depends on how your specific lumberyard prices its stock — many price by nominal dimension even though the actual finished board is slightly smaller. Confirm with your supplier which convention they use before finalizing a large order based on your calculation.
Should I order extra beyond the exact calculated board footage?
It’s generally wise to add a reasonable waste buffer for cutoffs, defects, and mistakes, especially for a project with many precise cuts — exactly how much extra depends on the project’s complexity, but ordering precisely the bare minimum leaves no room for error.
Final thought
Board feet is a volume calculation, not a length one — get all three dimensions and the quantity right, and pricing out a lumber order becomes a quick, accurate calculation instead of a guessing game at the yard.