Board Foot Calculator

A board foot calculator measures the volume of lumber so you can price and order it correctly. Enter the thickness, width, length, and quantity of your boards above to get the total board feet — and the cost if you add a price per board foot. It’s an essential tool for woodworkers buying hardwood, which is almost always sold this way.

What Is a Board Foot?

A board foot is a unit of volume used to measure and price lumber, especially hardwood. One board foot equals 144 cubic inches — for example, a piece one inch thick, twelve inches wide, and twelve inches long. Because it’s a measure of volume rather than length, it accounts for thickness and width as well as length, which is why a thick, wide board contains more board feet (and costs more) than a thin, narrow one of the same length. Lumberyards price hardwood by the board foot because boards come in so many different dimensions that pricing by the piece or by length alone wouldn’t be fair. Knowing how to calculate board feet lets you compare prices, budget a project, and order the right amount.

How to Use This Calculator

1. Enter the thickness and width of the board in inches.
2. Enter the length in feet.
3. Enter the quantity of identical boards.
4. Optionally enter a price per board foot to estimate the total cost.

How It Is Calculated

The standard formula, when length is in feet, is thickness (inches) times width (inches) times length (feet), divided by twelve. That divisor of twelve comes from the geometry of a board foot — it’s the shortcut that converts those mixed units into board feet directly. The calculator works out the board feet for a single piece, then multiplies by your quantity for the total. If you enter a price per board foot, it multiplies the total board feet by that price to estimate cost. So a one-inch by six-inch by eight-foot board works out to four board feet, and ten of them would be forty board feet.

Nominal vs. Actual Dimensions

One thing that confuses people is the difference between nominal and actual lumber dimensions, and it directly affects board-foot math. Softwood lumber is usually described by its nominal size — a “two by four,” for instance — but the actual, finished board is smaller, because it shrinks when it’s dried and planed smooth. Hardwood is often described by its rough thickness in quarters of an inch (“four-quarter” or 4/4 meaning roughly one inch rough), and may be sold rough or surfaced. The key is consistency: calculate board feet using the same dimensions your supplier uses to price the wood. If they price by nominal or rough size, use that; if they price by the actual surfaced dimensions, use those. Mixing the two is a common source of estimating errors. It’s also wise to buy a little more than the bare calculation suggests, because real projects lose material to saw kerfs, defects you cut around, planing, and the occasional mistake — many woodworkers add anywhere from 15 to 30 percent depending on the project and the grade of lumber. The calculator gives you the precise board footage of your finished parts; add your own waste allowance on top before you place the order.

Tips and Common Mistakes

• Keep length in feet and thickness/width in inches to match the standard formula.
• Use the same nominal-or-actual dimensions your supplier prices by.
• Add a waste allowance (often 15–30%) for cuts, defects, and mistakes.
• Remember hardwood thickness is often given in quarters (4/4, 5/4, 6/4, 8/4).
• Board feet measure volume, so thicker and wider boards cost more for the same length.

Buying Hardwood Lumber Confidently

Walking into a hardwood supplier is a lot less intimidating once board feet make sense, and a few extra habits will save you money and frustration. First, understand how the wood in front of you is being sold. Hardwood is commonly priced per board foot and described by rough thickness in quarters — 4/4 for roughly one inch, 5/4, 6/4, 8/4 and so on — and it may be sold rough-sawn or already surfaced (planed) on one or both faces and edges. A rough board measured before planing will yield slightly thinner finished stock, so if you need a specific final thickness, start with rough material a step thicker and plan to lose some in milling. Always calculate board feet using the same dimensions the yard uses to price the wood, or your budget will drift. Second, build in waste deliberately. The board footage of your finished parts is not the amount to buy: saw kerfs remove material with every cut, boards have knots, checks, and sapwood you cut around, and mistakes happen, so adding a generous margin — often 15 to 30 percent depending on the project, the board grade, and how much you can work around defects — keeps you from running short on a wood you may not be able to exactly match later. Third, inspect boards before buying, sighting down their length for cup, bow, and twist, since a cheap board you cannot flatten is no bargain. Finally, keep your cut list and this calculator handy at the yard: knowing the board feet of your parts, your waste allowance, and the price per board foot lets you estimate the cost of a stack on the spot and compare suppliers with confidence. A little preparation turns board-foot pricing from a source of confusion into a straightforward, fair way to buy exactly the lumber your project needs.

Frequently Asked Questions

How do I calculate board feet? Multiply thickness (in) × width (in) × length (ft) and divide by 12 for each board, then multiply by quantity. The calculator does it for you.

What is a board foot? A unit of lumber volume equal to 144 cubic inches — for example, a 1″ × 12″ × 12″ piece. It’s how most hardwood is priced.

What does 4/4 mean? It’s rough hardwood thickness in quarter-inches: 4/4 is roughly one inch, 8/4 roughly two inches. Use the thickness your supplier prices by.

Should I order extra? Yes. Saw kerfs, defects, planing, and mistakes all consume material, so many woodworkers add 15–30% over the calculated board feet.

Why is lumber priced by the board foot? Because boards vary so much in thickness, width, and length that a volume measure is the only fair way to price and compare them.

This tool provides estimates only. Confirm how your supplier measures and prices lumber before ordering.