The board foot formula
Board feet = thickness × width × length ÷ 144, with all three in inches. With the length in feet, divide by 12 instead. Thickness is the nominal size, the one the board is sold as, so a 4/4 board counts as a full inch even though it planes down to about 13/16".
The calculator works the way Handyman Calc does: each size is rounded to the nearest sixteenth, the board feet are kept as an exact fraction, and the cost is rounded to the cent once, on the whole order. A 1 × 5 that's 8 ft long is 3 1/3 board feet, which is $20.00 at $6.00, not $19.98.
For one board at a time, the board feet chart has common lumber at 8, 10, 12 and 16 ft and hardwood from 4/4 to 12/4, with a PDF to print.
On your phone, on the job site
On a phone, Handyman Calc has this board foot screen, plus a cut list that packs your pieces onto stock lengths, and thirteen more calculators. It works with no signal, and it's free.
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Charts worked out with the same math:
- how many bags of concrete a slab takes
- how many sheets of drywall a room takes
- a fraction to decimal chart for inches
- how much paint a room takes
- how much mulch a bed takes
- a roof pitch chart
- how many steps a rise takes
- the diagonal that squares a frame
- board feet for common lumber
More calculators:
Frequently asked questions
How do you calculate board feet?
Multiply thickness in inches by width in inches by length in inches, and divide by 144. Or, with the length in feet: thickness times width times feet, divided by 12. A 1 × 6 that's 8 ft long is 1 × 6 × 8 ÷ 12 = 4 board feet.
What is a board foot?
A piece of wood a foot square and an inch thick: 144 cubic inches. Hardwood is sold by the board foot. Most construction lumber is sold by the piece instead.
Do you use the actual or nominal thickness?
Nominal, the size the board is sold as. A 4/4 board planes to about 13/16", but it's priced as a full inch. Using the planed size undercounts what you paid for.
What does 4/4, 5/4 and 8/4 mean?
Thickness in quarters of an inch: 4/4 is 1", 5/4 is 1 1/4", 6/4 is 1 1/2" and 8/4 is 2". Type them that way in the thickness box and the calculator reads them as inches.
How do I price lumber by the board foot?
Total the board feet, then multiply by the price per board foot. The calculator keeps the exact fraction and rounds to the cent once, on the whole order, so 66 2/3 board feet at $6.50 is $433.33.
Does this work for logs?
No. It's for sawn boards. Standing trees and logs are estimated with log rules such as Doyle or Scribner, which allow for the saw kerf and slab waste, so they give a different number.