Board Foot Calculator

To find board feet, multiply thickness × width × length in inches and divide by 144. A board 1 in thick, 6 in wide and 8 ft (96 in) long is 1 × 6 × 96 ÷ 144 = 4 board feet. This board foot calculator works through a whole cut list, reads quarter thicknesses such as 8/4, knows nominal lumber sizes, and adds waste and cost.

How to use the board foot calculator

1. Name the first board and type its thickness and width in inches. Fractions and quarters are fine: 3/4, 1 1/2 and 8/4 all work.
2. Or pick a size from the list. Softwood sizes such as 2×4 fill in the nominal thickness and width and show the actual dressed size underneath. Hardwood sizes such as 8/4 set the thickness.
3. Type the length in feet, inches or both, the number of pieces, and the price per board foot if you know it.
4. Add a line for every part of the project, then set the extra for waste.

The result gives total board feet, the amount to buy with waste, the cost, linear feet and volume, plus a cut list table. Show steps writes out the multiplication for every line. Switch to metric to enter millimeters and meters; the answer stays in board feet, with cubic meters beside it.

Board foot formula

A board foot is the volume of a piece 1 in thick, 12 in wide and 12 in long: 1 × 12 × 12 = 144 cubic inches. Any board can be measured against that block:

All three give the same answer. The second form is quicker for lumber, because lengths are sold in feet: a 2×6 that is 10 ft long is 2 × 6 × 10 ÷ 12 = 10 board feet. Multiply by the number of pieces for the total, and by the price per board foot for the cost. Twelve board feet make one cubic foot.

Worked example: a hardwood tabletop

A tabletop needs four boards of 8/4 walnut, each 6 in wide and 8 ft long, at $9.50 a board foot.

1. Thickness: 8/4 means eight quarters of an inch, so 8 ÷ 4 = 2 in.
2. Length: 8 ft × 12 = 96 in.
3. One board: 2 × 6 × 96 ÷ 144 = 8 board feet.
4. Four boards: 8 × 4 = 32 board feet, and 32 × $9.50 = $304.00.

Worked example: 2×4 studs, nominal and actual

Ten 2×4 studs, 8 ft long, come to 2 × 4 × 96 ÷ 144 ≈ 5.33 board feet each, or about 53.33 board feet in all. That is the figure a lumberyard bills, because the American Softwood Lumber Standard counts board feet on the nominal size. The wood you carry home is smaller: a dry 2×4 is dressed to 1 1/2 × 3 1/2 in, so the actual volume is 1.5 × 3.5 × 96 ÷ 144 × 10 = 35 board feet, about 66% of the nominal figure.

Worked example: adding waste

Three 5/4 boards are 7 1/2 in wide and 10 ft 6 in (126 in) long. Each is 1.25 × 7.5 × 126 ÷ 144 ≈ 8.20 board feet, so the three come to about 24.61 board feet. Hardwood often has knots, checks or wane to cut around, so with 20% extra you would buy about 24.61 × 1.2 ≈ 29.53 board feet.

Nominal vs actual lumber sizes

Softwood lumber is named by its nominal size, the rough size before drying and planing. The finished boards are smaller. These are the minimum dressed dry sizes in Table 3 of the American Softwood Lumber Standard, PS 20-25, published by NIST. Board feet per linear foot use the nominal size, as the standard specifies.

Green (wet) lumber is dressed slightly larger, for example 1 9/16 × 3 9/16 in for a green 2×4. To price a length, multiply the last column by the length in feet: a 2×8 that is 12 ft long is 1.333 × 12 = 16 board feet.

Quarter notation: 4/4, 5/4, 8/4

Hardwood thickness is given in quarters of an inch. Read the fraction as inches: 4/4 is 1 in, 5/4 is 1 1/4 in, 6/4 is 1 1/2 in, 8/4 is 2 in, 12/4 is 3 in and 16/4 is 4 in. These are rough-sawn thicknesses, and hardwood dealers usually tally board feet on them. Boards that have been planed (surfaced) are thinner, and the exact surfaced thickness varies by mill, so ask the seller and use the quarter size for board feet unless the seller bills on the surfaced size. A handy shortcut: board feet per square foot of face equals the thickness in inches, so 1 sq ft of 8/4 is 2 board feet.

How much extra lumber to buy

The cut list is the wood that ends up in the project. You lose more than that to saw kerf, planing, end checks, knots you cut around and the odd mistake. The calculator starts at 15% extra. That is a starting point, not a rule: clear, straight stock for simple cuts needs less, while rough hardwood with defects or a project with lots of short parts needs more. Change the percentage to suit the boards in front of you.

Common board foot mistakes

• Mixing feet and inches. Divide by 144 when all three sizes are in inches, by 12 when the length is in feet. Using 144 with the length in feet gives an answer 12 times too small.
• Using actual sizes for softwood prices. Lumberyards bill a 2×4 as 2 × 4, not 1.5 × 3.5.
• Reading 8/4 as 8 in. 8/4 is 2 in.
• Forgetting the piece count. The formula gives one board; multiply by the number of boards.
• Confusing board feet with linear feet. A linear foot is just length. A 1×12 has 1 board foot per linear foot; a 1×4 has only a third of one.

Board feet practice quiz: 10 questions

Test yourself with 10 multiple-choice questions. Choose an answer and press Submit to see if you are right and why. Your score appears at the end.

Frequently asked questions

How many board feet are in a 2×4×8?

2 × 4 × 8 ÷ 12 ≈ 5.33 board feet, using the nominal size, which is how softwood is billed. The actual dressed board, 1 1/2 × 3 1/2 in, holds 3.5 board feet of wood.

What does 4/4 mean in lumber?

It means four quarters of an inch, so 1 in thick, measured rough-sawn. 5/4 is 1 1/4 in, 6/4 is 1 1/2 in and 8/4 is 2 in.

How do I convert board feet to linear feet?

Divide the board feet by the board feet per linear foot, which is thickness × width ÷ 12. For 1×6 boards that is 1 × 6 ÷ 12 = 0.5, so 30 board feet of 1×6 is 30 ÷ 0.5 = 60 linear feet.

How many board feet are in a cubic foot?

Twelve. A cubic foot is 12 × 12 × 12 = 1,728 cubic inches, and 1,728 ÷ 144 = 12.

How do you calculate board feet in a log?

Logs are estimated with log rules such as the Doyle, Scribner and International 1/4-inch rules, which allow for the round shape and sawing losses and give different answers for the same log. This calculator measures sawn boards; for standing timber or logs, ask the mill which rule it uses.

Related calculators

• Volume calculator for cubic inches, feet and other solids
• Square footage calculator for floor and panel areas
• Fraction calculator for adding sizes like 5 1/2 + 3/4
• Length converter for inches, feet, millimeters and meters
• Stair calculator for stringers, risers and treads

Sources

• NIST, Voluntary Product Standard PS 20-25, American Softwood Lumber Standard (January 2025): Section 2.2 board measure (board feet on nominal sizes) and Table 3, nominal and minimum dressed sizes. Checked November 2026.