How to Calculate Board Feet of Lumber and Cost

 

To calculate board feet of lumber, multiply thickness in inches by width in inches and length in feet, divide by 12, then multiply by the number of pieces. Add the volumes of separate lots before multiplying by a shared price per board foot.

Use the Board Foot Calculator for up to four lots. It calculates the volume represented by your entered dimensions. It does not determine a cutting list, convert nominal sizes automatically, or predict how much usable lumber a log will yield.

What is a board foot?

One board foot equals 144 cubic inches. Imagine a rectangular piece 1 inch thick, 12 inches wide, and 12 inches long: that piece contains one board foot. The unit measures volume, even though its name can sound like a length measurement.

Because a cubic foot contains 1,728 cubic inches, it contains 12 board feet. One board foot also equals exactly 0.002359737216 cubic meters. These conversions describe geometric volume, not supplier tally rules or the amount of finished material available after processing.

Measure thickness, width, and length consistently

For the imperial formula, thickness and width must be in inches while length is in feet. A board measured at 1 inch thick, 6 inches wide, and 8 feet long contains 1 x 6 x 8 / 12 = 4 board feet.

Enter fractions as decimals. Half an inch is 0.5 inch, and 8 ft 6 in is 8.5 ft. Do not enter 8.6 ft for that length. In metric mode, thickness and width are millimeters and length is meters; the calculator converts the resulting rectangular volume to board feet.

Add piece quantities and separate lots

Ten boards with the dimensions above contain 40 board feet. Suppose another lot contains five boards measured at 2 inches thick, 8 inches wide, and 10 feet long. Each contains 2 x 8 x 10 / 12 = 13.3333 board feet, so the second lot contains approximately 66.6667 board feet.

The combined unrounded volume is approximately 106.6667 board feet. Keep different dimensions on separate lines, with the correct quantity on each line. A mixed stack cannot be represented accurately by entering one convenient width unless that width is a valid basis for the intended calculation.

Calculate price without rounding each line early

At an illustrative shared price of $5 per board foot, the two-lot example costs $533.33 when the final amount is rounded once to cents. This price is an arithmetic example, not a current market rate. The calculator applies one shared rate; calculate lots priced differently in separate estimates.

Displayed line volumes are rounded for readability. Multiplying those rounded displays can differ slightly from multiplying the original volume. Supplier invoices may also use their own tally precision, minimum quantities, or billing increments, so confirm those terms before expecting the estimate to match an invoice exactly.

Actual dimensions and billed dimensions are different questions

For geometric volume, use the actual rectangular measurements you want to evaluate. For purchase cost, confirm which dimensions the supplier uses for billing. A nominal stock description may differ from the finished cross-section, and a hardwood thickness designation does not establish every finished measurement.

The calculator makes no automatic nominal-to-actual adjustment. Using smaller finished dimensions when a supplier bills another documented basis can understate the purchase estimate. Save the product description, dimensional basis, and quoted rate together so the result remains understandable later.

Do not confuse volume with coverage or usable yield

Square feet measure area. You need thickness to convert that area to board feet. Linear feet measure length, so you need both width and thickness. Even equal board-foot totals can represent different lengths and widths that are not interchangeable for a project.

A log or standing tree needs a separate yield method rather than this rectangular-board formula. Likewise, defects, trimming, saw cuts, and the required finished pieces affect how much stock you need to purchase. This calculator does not optimize cuts or add an automatic allowance.

Check the full purchase cost

Ask whether delivery, tax, milling, surfacing, or finishing are included in the quoted rate. Confirm any minimum order or tally convention. For a deck surface purchased by boards or area coverage, use the Composite Decking Cost Calculator separately; board-foot volume alone does not establish installed coverage or structural suitability.