Lumber
Board Foot & Lumber Cost Calculator
Quickly calculate the volume of your rough or surfaced lumber. Enter the dimensions of your boards and the price to instantly get the total volume in Board Feet (BF)in Cubic Meters (m³) and the total estimated cost.
Lumber Dimensions
Can use quarters like 4/4 or 5/4
e.g. 96 for an 8-foot board
Calculation Results
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How lumber volume is calculated
Lumber volume measures the physical amount of wood in a board, which dictates how the mill prices it. In North America, volume is measured in Board Feet (BF).In most of the world, volume is measured in Cubic Meters (m³). The formula is straightforward but relies on precise unit conversion.
Board Feet Formula
One Board Foot (BF) is exactly 144 cubic inches of wood (a 1" × 12" × 12" block). To calculate BF, multiply the thickness, width, and length in inches, then divide by 144.
Total Cubic Inches = Thickness" × Width" × Length"
Board Feet (BF) = Total Cubic Inches ÷ 144
Example: A 4/4 (1") board that is 6" wide and 96" long has 576 cubic inches. 576 ÷ 144 = 4 BF.
Lumber Cost
Mills and hardwood dealers price their stock "per Board Foot". Multiply your total BF by this price to get the board's cost.
Total Cost = Board Feet × Price per BF
Example: 4 BF × $8.50/BF = $34.00.
The Hardwood "Quarter" System
In North America, rough hardwood thickness is measured in quarters of an inch. A "4/4" board was 1 inch thick when it was rough sawn at the mill. By the time it is surfaced smooth on both sides (S2S) at the lumber yard, it will be thinner. Always use the original rough thickness (the quarters) when calculating board feet to estimate price, since that's what the mill charges for.
| Name | Rough Thickness (Used for BF) | Typical Surfaced Thickness (S2S) |
|---|---|---|
| 4/4 ("Four-quarter") | 1" | 13/16" or 3/4" |
| 5/4 ("Five-quarter") | 1-1/4" | 1-1/16" or 1" |
| 6/4 ("Six-quarter") | 1-1/2" | 1-5/16" or 1-1/4" |
| 8/4 ("Eight-quarter") | 2" | 1-13/16" or 1-3/4" |
| 12/4 ("Twelve-quarter") | 3" | 2-13/16" or 2-3/4" |
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Frequently Asked Questions
What is a board foot?
A board foot is a unit of volume for lumber in the United States and Canada. It is equal to the volume of a board that is 1 inch thick, 12 inches wide, and 12 inches long (144 cubic inches).
How do you calculate board feet?
Multiply the thickness in inches, the width in inches, and the length in inches, then divide by 144. If you measure the length in feet, divide by 12 instead.
What does 4/4 mean in lumber?
Hardwood lumber thickness is traditionally measured in quarters of an inch. "4/4" (four-quarters) means the rough board was 1 inch thick before surfacing. After surfacing (planing), a 4/4 board is typically 13/16" or 3/4"20mm or 19mm thick.
Do I calculate volume using rough or surfaced dimensions?
When buying lumber, always use the rough thickness (e.g. 1" for 4/4 stock) to calculate volume, even if the board has been surfaced down to 3/4". You are paying for the volume of wood that went into the planer! However, for width and length, you typically measure the actual usable size of the board you are holding.
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