Board Foot Calculator

How to measure

Read thickness as rough quarters

Hardwood is sold by the rough thickness, named in quarters of an inch. 4/4 is 1 inch, 5/4 is 1 1/4, 6/4 is 1 1/2, and 8/4 is 2 inches. Measure the board before it is planed, or pick the quarter that was billed. If the board is already surfaced on two sides, do not type the thinner dressed size into a rough-quarter field. Choose the S2S preset that matches the dressed thickness. The 4/4 S2S preset is 13/16 inch actual, and a lumberyard tally still bills it as 4/4 rough.

Measure width on a taper

Width is the actual face width in inches, including a fraction. On a board that narrows, measure at one third of the length from the narrow end, where the mark is on the diagram. Do not average the two ends, and do not measure the wide end. A straight board can be measured anywhere along the face.

Measure length in feet

Length is in feet, not inches. A board marked 8 feet is entered as 8, even if the stick runs a little past the mark. Nominal softwood such as a 2x4 uses the name size, 2 by 4 inches, not the dressed 1 1/2 by 3 1/2. The yard bills the name. Add a row for each size, set the quantity, and type a price per board foot only on the rows you are buying.

Formula

Board feet equal thickness in inches, times width in inches, times length in feet, divided by 12, times the quantity. Waste is a percent added to that total when you want the amount to buy. The price uses the same percent only while Include waste in the price is on. Turn that switch off and the cost stays on the exact board feet, while the buy quantity still includes waste.

Lumberyard tally follows hardwood practice. It drops the extra inches past a whole foot, rounds the surface measure, and uses the rough thickness. A half surface measure alternates up and down through the list, one piece at a time. Nominal softwood stays on its name size, because that tally is a hardwood rule.

Three 8/4 boards, 6 inches wide and 8 feet long, at $6.50 per board foot are 24.00 board feet and $156.00. At 15% waste the buy quantity is 27.60 board feet and the price is $179.40.

Common mistakes

• Entering a 2x4 as the dressed 1 1/2 by 3 1/2 instead of the nominal 2 by 4.
• Typing the length in inches. The length field is in feet.
• Measuring a tapered board at the wide end, or averaging the two ends.
• Typing a planed thickness such as 13/16 as rough 4/4, or the reverse.
• Rounding each row yourself. Lumberyard rounding is applied to each piece, and a .5 surface measure alternates.