Board Foot Calculator (Lumber Volume & Cost)

1. Measure the thickness in inches. This is the thinnest dimension of the board, the one you see edge-on. Use the actual (surfaced) thickness unless your mill bills by the nominal size: a 2×4 is really 1.5 × 3.5 inches, but many yards charge hardwood by the rough thickness, which is the nominal one. If in doubt, ask how your supplier invoices. 2. Measure the width in inches. This is the widest face of the board. With hardwood the width is often irregular board to board; take the average or calculate each piece separately. 3. Measure the length in feet. Unlike the previous two, length goes in feet, not inches. If your board is 8 feet 6 inches, enter 8.5. 4. Enter the number of identical pieces. If all your boards share the same dimensions, put how many there are and the calculator multiplies the result. For boards of different sizes, calculate each group separately and add the board feet. 5. Add the price per board foot (optional). Leave it at 0 if you only care about volume. With a price, the tool multiplies the total board feet by that value and gives you the estimated material cost.

The result panel shows the order's total board feet and the estimated cost side by side, so you can compare quotes from several lumberyards expressed in the same unit.

The formula is always the same: board feet = thickness (in) × width (in) × length (ft) ÷ 12 × quantity, and the cost = board feet × price per board foot. The divisor 12 appears because a board foot is 144 cubic inches and here the length is in feet (12 inches): thickness × width × (length × 12) ÷ 144 simplifies to thickness × width × length ÷ 12.

Here are five cases worked step by step:

• Surfaced oak lot. 10 boards of 1.5 in thick, 7.25 in wide, and 8 ft long, at 5.50 per board foot. Per board: 1.5 × 7.25 × 8 ÷ 12 = 7.25 board feet. With 10 pieces: 72.5 board feet. Cost: 72.5 × 5.50 = 398.75.
• A single thin board. 1 piece of 0.75 in × 5.5 in × 6 ft, no price (0). Calculation: 0.75 × 5.5 × 6 ÷ 12 = 2.0625 board feet. Cost: 0.
• Large walnut order. 25 boards of 2 in × 12 in × 10 ft at 4.25 per board foot. Per board: 2 × 12 × 10 ÷ 12 = 20 board feet. Total: 500 board feet. Cost: 500 × 4.25 = 2,125.
• Sample 1×6 plank. 1 piece of 1 in × 6 in × 8 ft at 3 per board foot. Calculation: 1 × 6 × 8 ÷ 12 = 4 board feet. Cost: 4 × 3 = 12.
• Dining table project. 50 boards of 1.5 in × 9.25 in × 12 ft at 6.80 per board foot. Per board: 1.5 × 9.25 × 12 ÷ 12 = 13.875 board feet. Total: 693.75 board feet. Cost: 693.75 × 6.80 = 4,717.50.

Notice that doubling the thickness or the width doubles the board feet, while the divisor 12 keeps the scale manageable: a typical furniture board rarely exceeds 15 board feet per piece.

A board foot is a unit of volume, not of area or length. By definition, it equals a block of wood of 1 inch × 12 inches × 12 inches = 144 cubic inches. Any combination of dimensions that yields those 144 cubic inches is one board foot: a board of 2 in × 6 in × 12 in, one of 1 in × 6 in × 24 in, or one of 4/4 (one inch) × 12 in × 12 in are all worth exactly the same. That is why the board foot is so convenient in the lumber trade: it lets you compare and bill boards of very different thicknesses and widths with a single number.

Why the length is in feet. In US sawn lumber, thickness and width are small and measured in inches, but the length of boards is given in feet. To avoid juggling three different units, the classic formula keeps the length in feet and divides by 12: thickness (in) × width (in) × length (ft) ÷ 12. It is exactly equivalent to converting the length to inches (× 12) and dividing by 144 cubic inches; both versions give the same result.

The quarter system (4/4, 5/4, 8/4). Hardwood is often sold by its rough thickness expressed in quarter-inches: 4/4 means one inch, 5/4 one and a quarter inches, 8/4 two inches. When entering the thickness in the calculator, use the matching decimal value (4/4 = 1; 5/4 = 1.25; 8/4 = 2). It pays to know whether your supplier bills by the rough nominal thickness or the final surfaced thickness, because the difference — on the order of a quarter inch — changes the total board feet and therefore the price.

Board foot versus the metric system. Outside North America, wood is almost always sold by the cubic meter or by the linear meter. For reference, 1 board foot equals about 2,360 cm³, that is, 0.00236 m³; put another way, 1 cubic meter is roughly 424 board feet. If you buy in a metric market but follow a US plan, this equivalence lets you translate the volume without redoing the whole calculation. The board foot is always a volume of wood, not the surface it will cover once planed and assembled.

Picture walking into a sawmill to buy oak boards: the price is not per meter or per piece, but per "board foot." A board foot is the standard unit of volume for sawn lumber in the United States and Canada, equal to a board 1 inch thick, 12 inches wide, and 12 inches long — in other words, 144 cubic inches of wood. This calculator turns the real dimensions of your boards — thickness and width in inches, length in feet — into the total board feet you need, multiplies by the number of pieces, and, if you enter a price per board foot, returns the estimated cost of the order. It is the tool woodworkers, cabinetmakers, and DIY hobbyists use to budget solid lumber without confusing inches with feet or overpaying on a rough guess.