How to use this calculator
- Enter board dimensions. Use actual thickness, width and length for the lumber being bought or tallied.
- Enter quantity. Set the number of identical boards.
- Add waste and price. Use waste for defects, trimming and kerf, then enter price per board foot if you want a cost estimate.
- Read board feet and cost. Review total board feet, net volume, waste allowance and estimated lumber cost.
How it works
A board foot is a lumber volume unit equal to one square foot of board that is one inch thick. The standard formula is: board feet = T(in) x W(in) x L(ft) / 12 The calculator multiplies by quantity, then adds the waste or overage percentage before estimating cost.
This is a material-tally tool, not a structural sizing tool. For metal and other stock weights, use the metal weight calculator. For stiffness or span checks, use the beam deflection calculator or LVL beam calculator.
Worked example
Verified against the live calculator
A board that is 1 in thick, 6 in wide and
8 ft long contains 1 x 6 x 8 / 12 = 4 board feet.
Ten of those boards contain 40 board feet. With a
10% waste allowance, buy 44 board feet. At
$6.25/bd ft, the estimated lumber cost is $275.
Frequently asked questions
How do you calculate board feet?
Board feet = thickness in inches * width in inches * length in feet / 12. Multiply by quantity, then add any waste or overage allowance.
Should I use nominal or actual lumber size?
Use the dimension you are buying or tallying. Hardwood and rough lumber are often sold by actual thickness and width, while construction lumber nominal sizes are smaller after dressing.
How many cubic feet are in a board foot?
One board foot is 144 cubic inches, or 1/12 cubic foot. It is the volume of a board 1 inch thick, 12 inches wide and 12 inches long.
Does waste include saw kerf?
Use the waste field for kerf, trimming, defects, matching grain, sorting and any overage you want to buy. For detailed cutting, use a cut list or optimizer.
Does this work with metric dimensions?
Yes. Toggle SI in the header to enter millimetres and metres; the calculator converts to the standard board-foot formula internally.
Method & assumptions
- Uses actual entered dimensions; nominal/dressed-size assumptions are not inferred.
- Waste allowance is applied after quantity, so it increases total board feet and cost.
- Cost is a simple price-per-board-foot estimate before tax, surfacing, delivery or minimum-order charges.
- Defects, grade yield, live-edge slabs, taper, moisture shrinkage and cut-list optimization need separate handling.