Lumber Board Feet Calculator
Estimate lumber volume in board feet from a piece thickness, width, length, quantity, and optional waste allowance. The board-foot measure is a volume convention used for sawn lumber; it is not the same as a linear foot or square foot, and the estimate depends on the dimensions you enter.
How to use this calculator
- Enter thickness and width in inches and length in feet; keep all piece dimensions in those units.
- Enter the number of matching pieces and add a waste allowance that reflects cuts, defects, and your project plan.
- Compare the result before and after the allowance, then confirm nominal versus actual sizes with your lumber supplier.
Board-foot formula
Board feet per piece = thickness (in) × width (in) × length (ft) ÷ 12. Order estimate = board feet per piece × piece count × (1 + waste percentage ÷ 100).
- One board foot is a volume of 144 cubic inches, approximately 0.002359737216 cubic metres.
- The waste percentage is applied after calculating the total for the pieces. It is an allowance, not a prediction of actual scrap.
Worked examples
Worked example: 25 boards
For 1.5-inch thickness, 5.5-inch width and 8-foot length, one piece is 5.5 board feet.
5.5 × 25 = 137.5 board feet. With a 10% allowance: 137.5 × 1.10 = 151.25 board feet.
The planning order quantity is 151.25 board feet before supplier rounding or packaging rules.
Understanding the result
Use the pre-waste total to understand the volume represented by the dimensions; use the allowance-adjusted total for a planning estimate.
If you mix different sizes or species, calculate each group separately and then combine totals.
Important notes
Board-foot estimates use the dimensions entered, which may be nominal rather than actual dressed dimensions. Confirm supplier measurements, species, grading, and cutting plans before ordering.
Structural lumber selection, span, grading, and load requirements are not determined by this volume calculator.
Frequently asked questions
What is a board foot?
One board foot represents 144 cubic inches of lumber volume. A common formula using inches for thickness and width and feet for length is thickness × width × length ÷ 12.
How much waste should I add?
It depends on project geometry, cut patterns, defects, and how carefully stock can be reused. Choose an allowance that fits your project; this calculator does not prescribe a universal percentage.
Are nominal dimensions the same as actual dimensions?
Often not. Dressed lumber can have smaller actual dimensions than its nominal designation. Use dimensions appropriate to the purpose and confirm them with the supplier.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.