Board Foot Calculator
The lumber trade's volume unit, from nominal dimensions.
Work out Board Foot. The lumber trade's volume unit, from nominal dimensions. Free, with no account and nothing to download.
The number on the label, not the milled size.
Leave at zero to skip the cost.
Board feet
80.00
8.00 per piece × 10
A board foot is 144 cubic inches — nominally one inch thick, twelve wide and twelve long — so twelve board feet make a cubic foot. Use the nominal dimensions from the label rather than the milled ones: a 2×4 measures 1½ by 3½ but is priced as a 2×4, and calculating from the actual size understates the cost.
How the Board Foot Calculator works
A board foot is 144 cubic inches — nominally a piece one inch thick, twelve wide and twelve long. The word nominal is doing real work there: a 2×4 is milled to 1½ by 3½, and hardwood is almost always priced on the nominal dimensions rather than the actual ones. Which numbers to use is the whole difficulty, and the answer is the ones on the label.
Also known as: board feet calculator · lumber calculator · how to calculate board feet · bd ft calculator
The calculation itself
Thickness in inches times width in inches times length in feet, divided by twelve. The twelve looks arbitrary until you see where it comes from: a board foot is 144 cubic inches, and one of the three dimensions is in feet.
So twelve board feet make one cubic foot, exactly.
In practice
A 2×6 at eight feet: 2 × 6 × 8 ÷ 12 = 8 board feet. Ten of them is 80 board feet, which is 6.67 cubic feet of timber.
Hardwood thickness is quoted in quarters of an inch — 4/4 is one inch, 8/4 is two. A 4/4 board six inches wide and eight feet long is four board feet.
Nominal against actual
This is the whole difficulty. A 2×4 is milled to 1½ by 3½ inches, but it is sold, stocked and priced as a 2×4.
Calculate from the actual milled dimensions and you will understate the board footage by about a third — and the merchant will still charge on the nominal figure, so the estimate comes out wrong in the direction that hurts.
Use the numbers on the label. The exception is rough-sawn timber, which is genuinely the size it says, and where nominal and actual coincide.
Acting on it
Price by the board foot and compare across lengths. A longer board is often cheaper per board foot and generates fewer joins.
Add for waste separately. Board footage is what you buy, not what ends up in the work — rough lumber loses material to milling and defects, and cutting to length loses more.
Check whether a quote is nominal or actual before comparing two suppliers. They are not always quoting the same thing.
Frequently asked questions
How do I calculate board feet?
Thickness in inches times width in inches times length in feet, divided by twelve. A 2×6 at eight feet is 2 × 6 × 8 ÷ 12 = 8 board feet.
Is a board foot a measure of volume?
Yes — 144 cubic inches, so twelve board feet make one cubic foot. It is a volume unit that happens to be quoted in mixed units, which is why the division by twelve looks arbitrary until you see where it comes from.
Should I use nominal or actual dimensions?
Nominal, in almost every case — that is what the price is quoted against. A 2×4 measures 1½ by 3½ but is sold and priced as a 2×4, and calculating from the actual dimensions will understate the cost.
How do hardwood quarters work?
Hardwood thickness is quoted in quarters of an inch: 4/4 is one inch, 8/4 is two. So a 4/4 board six inches wide and eight feet long is four board feet.
Does board footage account for waste?
No, it is the volume of what you buy. Rough lumber loses material to milling and defects, and cutting to length loses more, so an allowance on top is normal.
Put this calculator on your own site
Free to use, on any site, commercial or not. Paste this where you want it to appear. It is a plain iframe, so it works in WordPress, Squarespace, Wix, Webflow, Ghost and anything else that accepts HTML.
<iframe src="https://www.thecalclibrary.com/embed/board-foot-calculator" width="100%" height="640" style="border:1px solid #e2e8f0;border-radius:12px" loading="lazy" title="Board Foot Calculator"></iframe>The only condition is that the credit line stays visible. It sits inside the frame, so you do not have to do anything to keep it.