What the Lumber Calculator Does
This Lumber Calculator works out how much wood you have in three different units at once: board feet, cubic feet, and cubic meters. It is built around the board-foot measurement system used widely in the United States and Canada for buying and pricing rough and dimensional lumber. Enter the dimensions of a single board and the number of boards, and the calculator returns the total volume for the whole batch — handy for estimating material costs, planning a delivery, or comparing quotes.
The Input Fields
- Length (feet) — the length of one board measured in feet.
- Width (inches) — the face width of the board in inches.
- Thickness (inches) — how thick the board is, in inches.
- Quantity — how many identical boards you are calculating.
Note the mixed units: length is entered in feet while width and thickness are in inches. This matches how lumber is traditionally described (for example, a "2×4×8" board).
The Formula
The core calculation is the standard board-foot formula:
- Board feet = (Length × Width × Thickness × Quantity) ÷ 144
- Cubic feet = Board feet ÷ 12
- Cubic meters = Cubic feet × 0.0283168
The standard board-foot formula is:
$$\text{Board Feet} = \frac{\text{Length (ft)} \times \text{Width (in)} \times \text{Thickness (in)} \times \text{Quantity}}{144}$$The 144 divisor converts the mixed feet-and-inches figures into board feet (one board foot equals 144 cubic inches of wood, i.e. \(1\ \text{ft} \times 12\ \text{in} \times 1\ \text{in}\)). Dividing by 12 turns board feet into true cubic feet, and the 0.0283168 factor converts cubic feet to cubic meters.
Worked Example
Suppose you have 10 boards, each 8 feet long, 6 inches wide, and 2 inches thick.
- Board feet = \((8 \times 6 \times 2 \times 10) \div 144 = 960 \div 144 =\) 6.67 board feet
- Cubic feet = \(6.67 \div 12 =\) 0.556 cubic feet
- Cubic meters = \(0.556 \times 0.0283168 =\) 0.0157 cubic meters
You could then multiply the board feet by your supplier's per-board-foot price to estimate the cost.
Frequently Asked Questions
What is a board foot? A board foot is a volume of lumber equal to 144 cubic inches — for example, a piece 1 foot long, 12 inches wide, and 1 inch thick. It is the standard unit for pricing hardwood and softwood in North America.
Should I use nominal or actual dimensions? For accurate volume, use the actual finished dimensions. A "2×4" is really about 1.5 × 3.5 inches after planing, so entering the nominal 2 and 4 will overstate the volume slightly.
Why is length in feet but width and thickness in inches? This mirrors how lumber is normally specified and described in the trade, and the formula's divisor of 144 is set up to handle that mix automatically.
