How do I calculate board feet from lumber dimensions?

Board feet equals thickness in inches times width in inches times length in feet divided by 12. Enter nominal lumber size and quantity; the calculator converts to board feet, linear feet, and estimated weight, and supports deck or fence planning mode.

What is a board foot in lumber?

A board foot measures 1 inch thick by 12 inches wide by 12 inches long, or 144 cubic inches of wood. The calculator accepts any nominal size, shows total board feet and linear feet for your quantity, and gives estimated weight.

How do I estimate lumber for decking or fencing?

Switch to deck or fence mode, enter area dimensions, board width, and spacing. The calculator estimates total boards, joists or rails, and material cost, building on the same board-foot and weight calculations from the lumber input mode.

Lumber

Lumber / Board Feet Calculator

Convert nominal lumber sizes into board feet, linear feet, and estimated weight with deck or fence planning support.

Lumber estimating gets easier when every board is converted to the same unit. This free board foot calculator helps DIYers and contractors turn thickness, width, length, and quantity into a usable lumber total. Use it to compare boards, build a cut list, and avoid mixing up nominal size with actual size.

How it works

A board foot is calculated from board thickness in inches, board width in inches, and board length in feet. The formula is: board feet = (thickness in × width in × length ft) / 12. Use actual lumber dimensions when you have them, not just the nominal name stamped on the board. For example, a 2x4 is actually 1.5 in × 3.5 in, so those are the numbers to enter for a real board-foot estimate. Linear feet are different: they measure length only, not volume. To estimate a project, calculate board feet for each board size, then multiply by the quantity of matching pieces and add the groups together.

Worked examples

Single actual 2x4 board (1.5 in × 3.5 in × 12 ft) / 12 = 5.25 board feet One actual 2x4 that is 12 ft long contains 5.25 board feet.
Twelve matching actual 2x4 boards 5.25 board feet × 12 boards = 63 board feet Twelve actual 2x4 boards, each 12 ft long, total 63 board feet.
Nominal 2x4 math compared with actual 2x4 math Nominal: (2 in × 4 in × 12 ft) / 12 = 8 board feet. Actual: (1.5 in × 3.5 in × 12 ft) / 12 = 5.25 board feet. Using nominal size overstates the board-foot amount for this 2x4, so actual dimensions give the cleaner estimate.

FAQ

What is the formula for board feet?

Use: board feet = (thickness in × width in × length ft) / 12. Thickness and width are entered in inches, while length is entered in feet.

Should I use nominal or actual lumber size?

Use actual size when estimating board feet. A 2x4 is commonly referred to by its nominal name, but its actual size is 1.5 in × 3.5 in, which changes the board-foot result.

Are board feet the same as linear feet?

No. Linear feet measure length only. Board feet measure lumber volume using thickness, width, and length, so they’re better for estimating rough lumber or comparing boards of different sizes.

How do I estimate total board feet for a project?

Group your lumber by matching thickness, width, and length. Calculate board feet for one piece in each group, multiply by the quantity of pieces in that group, then add the group totals together.