Board Foot Calculator

What is a board foot?

A board foot is a unit of volume for lumber, not length and not area. One board foot is a board 12 inches wide, 12 inches long, and 1 inch thick. That is 144 cubic inches of wood, or one square foot at one inch thick.

This matters because lumber is usually priced per board foot, not per board. Two boards can look similar on a rack and cost very different amounts, because their thickness, width, and length are different. Once you know the total board feet, you can compare quotes fairly, check a yard’s tally, and avoid overbuying expensive hardwood.

How to calculate board feet

If all your measurements are in inches, divide by 144 instead. Both formulas give the same answer. The calculator above does this for you, including quantity, waste, and price, so you do not have to do the maths by hand for a full order.

1. Measure thickness and width in inches, and length in feet. Write down whether you are using nominal sizes as billed, or actual measured sizes.
2. Multiply thickness x width x length, then divide by 12. That is the board feet for one board.
3. Multiply by quantity. That is the total board feet before waste.
4. Add waste for cuts, defects, and mistakes. The calculator shows total with waste separately.
5. Multiply total with waste by price per board foot. That is your estimated material cost.

Board foot worked examples

Start with a board you know, then scale up. A board 1 inch thick, 6 inches wide, and 8 feet long is (1 x 6 x 8) / 12 = 4 board feet. Five of those boards are 20 board feet. Add 10 percent waste and you need 22 board feet. At $8 per board foot, cost with waste is $176.

Use the table for a quick check, and use the calculator for a real order, because quantity and waste change the total.

Nominal vs actual lumber sizes: the trap to watch

Lumber is sold by nominal size, but the actual size after planing and drying is smaller. This is normal, and it is why two quotes can look confusing if one yard bills nominal and another bills actual.

Waste: how much extra lumber to buy

Buy extra for cuts, defects, knots, warp, and mistakes. A good starting point is 10 percent for simple projects with straight cuts, and 15 percent for rough hardwood, projects with many different cut lengths, or boards with visible defects you plan to cut around.

The calculator shows total with waste separately, so waste is never hidden inside the price. If you are buying expensive hardwood, keep offcuts, because a short offcut from one project is often the exact piece for the next small part.

Board foot cut list and price

For a full project, turn your cut list into board feet first, then price it. List every board by thickness, width, length, and quantity, run each size through the calculator, add waste, and multiply the total by price per board foot. This works for hardwood lumber as well as softwood, because the formula does not change, only the price per board foot changes. Use the board foot chart page to check a common size quickly, without recalculating every board.

Example cut list: ten boards at 1 x 6 x 8 ft are 40 board feet. Five boards at 2 x 4 x 8 ft, nominal, are 26.67 board feet. Together that is 66.67 board feet before waste, 73.33 board feet with 10 percent waste, and $586.67 at $8 per board foot. That is the kind of tally a yard will check, so bringing it in board feet saves time and avoids a pricing argument.

Hardwood vs softwood: does the formula change?

No. The board foot formula is the same for hardwood and softwood. What changes is how lumber is described and priced. Hardwood thickness is often described in quarters, so a 1 inch board is called 4/4, and a 2 inch board is 8/4. Softwood framing lumber is usually described by nominal size, like 2 x 4, even though the actual size is smaller.

Hardwood is also more likely to be sold rough, surfaced on two sides, or with defects that affect usable yield. That is why waste matters more on hardwood, and why you should check boards for warp, twist, knots, and cracks before loading them, not after you get home.

Board feet in a log

Logs use different rules from sawn lumber, including Doyle, Scribner, and International 1/4 inch. The same log can scale differently under each rule, so buyer and seller must agree on the rule before money changes hands.

Example: a log 12 inches in diameter and 16 feet long is 64 board feet under Doyle. Diameter is small-end diameter inside bark, and length is merchantable length. See the Log Board Foot Calculator for the full guide.

Common board foot mistakes

1. Forgetting waste, then running short on the last boards, which are often the most expensive to replace.
2. Mixing nominal and actual sizes in the same tally, so the total is wrong even though each board looks right.
3. Pricing per board instead of per board foot, so a wider or thicker board looks like a bad deal when it is not.
4. Measuring length in inches but dividing by 12, or measuring in feet but dividing by 144. Pick one system and stay with it.
5. Buying by square feet for a project that is priced by volume. Square feet ignore thickness, and thickness is where the cost lives.

Lumber buying checklist

Before you go to the yard, bring your cut list in board feet, with waste included. At the yard, ask: nominal or actual billing, price per board foot by species, minimum order, delivery fee, and return policy for defects. Check boards for warp, twist, knots, and cracks before loading. A cheap board that warps is not cheap, and a straight board at a fair price is the cheapest board in the long run.

Related lumber calculators

Frequently asked questions

Estimate only. Confirm with your supplier before ordering.