Board Foot / Lumber Calculator
Board feet and lumber cost from thickness, width and length.
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Results
Total board feet
80.00
8.000 board feet per piece × 10 pieces
Board footage is calculated on nominal rough dimensions. Surfaced lumber (S4S) is thinner and narrower than nominal but is still sold at the rough measure.
80.00 bd ft · $360.00
How this is calculated
A board foot is a volume measure: 144 cubic inches of lumber, equal to a piece one inch thick, twelve inches wide and one foot long. Because thickness and width are measured in inches while length is usually in feet, the standard formula divides by 12:
board feet = thickness(in) × width(in) × length(ft) ÷ 12
When every dimension is in inches, divide by 144 instead — that is what this tool does internally:
board feet = thickness(in) × width(in) × length(in) ÷ 144
Hardwood is graded in quarters of an inch: 4/4 is one inch, 5/4 is one and a quarter, 8/4 is two inches. Always use the rough nominal thickness in the calculation even if the board has already been surfaced, because that is how mills and yards price it.
Cost is simply total board feet multiplied by your price per board foot. Add a waste factor for defects, snipe and cutting — 15% is typical for rough lumber and 25% or more if you are working around knots and checks in character-grade stock.