Use the free Board Foot Calculator below: your data never leaves your browser — all work happens on your device, and nothing is uploaded to any server.
What this tool does
Lumber is often priced and sold by the board foot, a unit that confuses almost everyone the first time they meet it, because it mixes inches and feet in a single formula. This free board foot calculator removes the confusion: enter thickness and width in inches, length in feet, and quantity, and it gives board feet per board, the total, and the volume in cubic metres. It is a practical tool for pricing a project, comparing quotes, or checking a timber merchant’s maths before you pay.
Measure thickness and width in inches, using the nominal size the merchant quotes, and length in feet, then enter how many identical boards you need. Press Calculate and you will see the board feet for one board and for the whole lot, plus the cubic-metre equivalent. If your boards differ in size, run each size separately and add the totals, because mixing sizes in one calculation gives a meaningless average. Keep a note of each size’s result, so a quote that looks cheap per board can be compared fairly per board foot.
One board foot is a volume: a board one inch thick, twelve inches wide, and one foot long, which is one hundred and forty-four cubic inches. The formula is therefore thickness in inches times width in inches times length in feet, divided by twelve. A one-inch by six-inch board eight feet long is one times six times eight divided by twelve, which is four board feet. A two-inch by four-inch board eight feet long is two times four times eight divided by twelve, which is five point three three board feet. Cubic metres follow by multiplying board feet by zero point zero zero two three six.
Take a small shelf project needing ten boards of one inch by twelve inches by ten feet. Each board is one times twelve times ten divided by twelve, which is ten board feet, so ten boards total one hundred board feet, or about zero point two three six cubic metres. If the merchant charges five currency units per board foot, the timber costs five hundred, and you can see at once whether a cheaper board that is actually thinner or shorter is really cheaper. That per-board-foot comparison is the main reason the unit survives: it lets you compare boards of different sizes on equal terms.
Watch for nominal versus actual size, the classic board-foot trap. A board sold as two inches by four inches is often actually one and a half by three and a half inches after planing, and merchants may price on the nominal size, so ask which size a quote uses before you compare. Allow for waste as well: cutting, knots, warping, and end trimming mean you should buy roughly ten percent more than the finished project needs, more if the boards are rough or the cuts are complex. Store boards flat, stickered, and dry, because a board that warps after delivery is money lost even if the board-foot maths was perfect.
Why not just use cubic metres? You can, and this tool gives that figure too, but board feet remain the pricing unit in much of the timber trade, so knowing both avoids confusion at the counter. Does the formula work for metric boards? Yes, if you convert first: thickness and width in inches, length in feet, which the tool expects, so convert millimetres by dividing by twenty-five point four and metres by multiplying by three point two eight. Should I include waste in the board-foot total? Keep waste separate: calculate the finished boards first, then add your waste allowance, so you can see exactly how much is project and how much is spare.
Important limits: an estimate, not a code approval
Every result on this page is an educational estimate only. It is not professional advice and it does not guarantee compliance with any building, plumbing, gas, or safety code. Local rules, soil, climate, pipe material, and the condition of an existing system can change the correct answer, and this tool cannot see any of those things. Gas work must be done by a licensed professional and checked against local gas codes; never size, install, or alter gas pipework from an online estimate. For any real installation, repair, or purchase decision, consult a licensed plumber or carpenter first, and get a second opinion when the job is large, expensive, or safety-critical. Use this tool to plan, compare, and ask better questions — not as a substitute for a qualified person on site.
Also available in Spanish: Spanish version.