Free board foot calculator — for a whole lumber list, not one board
Most board foot calculators do one board at a time. This one takes the whole cut list: add each size, quantity and length, and it totals the board feet, adds your waste allowance and prices the order. No signup, no download.
What a board foot is
A board foot is a volume: 1 inch thick by 12 inches wide by 1 foot long, or 144 cubic inches. The formula is thickness (in) × width (in) × length (ft) ÷ 12. A 2 × 4 that is 8 ft long is 2 × 4 × 8 ÷ 12 = 5.33 board feet.
The catch is that board feet use nominal dimensions, which is how lumber is sold and priced. A 2 × 4 actually measures 1½ × 3½, but you pay for the 2 × 4. Hardwood is sold by quarters of an inch: 4/4 is 1" thick, 5/4 is 1¼", 6/4 is 1½", 8/4 is 2". Enter the nominal number and the calculator does the rest.
How to use it
1. Add a row per size. Pick a common size from the dropdown, or type thickness, width and length for anything else. Width can be left blank for hardwood you are buying by the board foot regardless of width.
2. Enter quantity. Board feet per piece × pieces.
3. Set your price. One price per board foot for the whole list, or override it on a row — hardwood and framing lumber are never the same number.
4. Waste. 15% is a normal allowance for hardwood (defects, sorting, cuts). Drop to 5–10% for framing lumber you can use whole.
How the math works
- Each row: thickness × width × length ÷ 12 = board feet per piece, times the quantity.
- Net board feet is the sum. The buy figure adds the waste percentage and rounds up once at the end.
- Cost = board feet × (1 + waste) × price per board foot, per row.
- The quick-reference table shows common dimensional sizes at 8, 10, 12 and 16 ft so you can sanity check a supplier's tally.
Worked example
Ten 2 × 4 × 8 studs are 53.33 board feet. At 15% waste you would buy 62 board feet, which at $4.50 per board foot is about $276. Twenty board feet of 8/4 walnut at $14 is $280 before waste — hardwood is where the number matters.
Turn it into a quote
Copy list puts the tally on your clipboard. For a framing package, run the fence calculator or the drywall calculator for the rest of the materials, then send the whole thing with the estimate generator. Pricing labor? See what carpenters earn by state.
FAQ
How do you calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12. Use nominal dimensions. A 1 × 12 × 10 ft board is 1 × 12 × 10 ÷ 12 = 10 board feet.
How many board feet are in a 2x4x8?
5.33 board feet. A 2 × 4 × 10 is 6.67, a 2 × 4 × 12 is 8, and a 2 × 4 × 16 is 10.67. The quick-reference table on the calculator lists the common sizes.
How many board feet in a 2x6x12?
12 board feet: 2 × 6 × 12 ÷ 12. Every 2 × 6 is exactly one board foot per foot of length, which is a handy check when a supplier hands you a tally.
Is a board foot measured on actual or nominal size?
Nominal. Lumber is sold on the nominal size even though a 2 × 4 measures 1½ × 3½. Rough-sawn hardwood is closer to nominal, which is why 4/4 stock is called one inch even after surfacing takes it to ¾ or ⅞.
What does 4/4, 5/4 and 8/4 mean?
Hardwood thickness in quarters of an inch, measured rough. 4/4 is 1 inch, 5/4 is 1¼, 6/4 is 1½, 8/4 is 2. Enter 1, 1.25, 1.5 or 2 as the thickness, or pick them from the dropdown.
How much waste should I add for hardwood?
15% is typical for hardwood once you allow for defects, sap, checking and sorting for grain. Go to 20–25% for highly figured wood or a job that needs long clear lengths. Framing lumber you can use whole needs only 5–10%.
Is this calculator free?
Yes, completely. No account, no email, no download. It runs in your browser and we never see your numbers.