Board Foot Calculator

The short answer

A board foot is 144 cubic inches — a board 12 inches square and 1 inch thick. A 2 by 4 that is 8 feet long is 5.33 board feet at nominal dimensions, or 3.5 board feet using the actual 1.5 by 3.5 inch section. Ten 2 by 6 boards at 10 feet give about 69 board feet actual, or 91 at nominal. Which basis you are buying on is the first thing to establish.

What it depends on

The nominal-versus-actual gap is the trap, and it is not a rounding error: a 2 by 10 is 1.5 by 9.25 inches, which is about 19% less wood than the nominal figure suggests. Hardwood is often sold by the quarter, where 4/4 means 1 inch rough thickness that finishes nearer 3/4 inch. Buying random lengths rather than specified lengths usually reduces waste and cost.

Where this stops being useful

This is a volume conversion and does not price the timber, which depends on species, grade, moisture content and region. Ordering waste, cutting allowance and the difference between rough and finished thickness all affect what you actually need. A supplier can quote against your actual take-off. General information and planning only, not engineering, structural or code advice.

Board foot is a volume measure, and two boards of the same total board feet can look completely different on the wall. A wide thin board and a narrow thick one can have identical volume but different structural behaviour and different coverage on a wall. For projects where the appearance or the span matters, work in linear feet of the actual board rather than volume. Board feet is the right unit for pricing and for total material, not for planning a cut list.

Board feet appear on every invoice and on every timber order form, which makes them worth understanding even though almost nobody thinks in them. Once the conversion is familiar it becomes obvious why a narrow board and a wide board of the same volume are not interchangeable.

A cut list, laid out by length, determines how many boards you actually need. Group every piece by length, then nest them — two eight-foot pieces and one four-foot piece come out of one ten-foot board, whereas buying them separately is the most common way people over-buy. Add a kerf allowance for every cut the blade makes. If the project involves a lot of small pieces, the kerf adds up surprisingly fast, and a ten to fifteen percent allowance is realistic.

Hardwood is sold by volume, not by length, because a board's price depends on how much timber it contains and that is a product of thickness, width and length together. The unit is the board foot: one square foot of lumber an inch thick, which is twelve inches by twelve inches by twelve inches. Thickness, width and length in inches and feet, multiplied together and divided by twelve, gives the board feet in a single piece. The formula is worth memorising because it lets you compare offers. A wide board costs more than a narrow one of the same length, even though both might be sold from the same stack, and a thicker board costs more again in proportion. When a supplier quotes a price per board foot, the total for your project is simply the total board feet multiplied by that rate, plus waste for the cuts your design requires. Rough lumber and surfaced lumber are not the same purchase. Rough stock is sold at nominal dimensions and often measures slightly over, while surfaced boards are planed down and measure slightly under — a nominal one-by-six may finish at three-quarters by five and a half inches. Pricing is normally based on the nominal size, so the board feet you pay for can exceed the usable volume, and it pays to know which convention your supplier uses. This calculator converts your pieces into board feet and total cost. It assumes all pieces are the same size, so run it once per size and add the results for a mixed order. Add a margin for waste and defects, since knots, checks and waney edges are common in hardwood and the usable yield is always less than the nominal volume.

This calculator returns estimates for planning and general information only. It is not engineering, architectural, structural, electrical or code advice, and it cannot replace a qualified professional who has seen the site. Material quantities depend on the actual dimensions, the product you buy and local building codes, so confirm the figures before ordering materials or starting work, and always follow local regulations.