A board foot calculator for woodworkers, cabinet makers and sawyers. Every figure labelled, the working shown, and quarter thicknesses handled rough or surfaced.
Board Foot Calculator₊ is coming soon to the App Store.
A board foot is 144 cubic inches: a piece one inch thick, twelve inches wide and twelve inches long. Multiply thickness in inches by width in inches by length in feet and divide by 12, or divide by 144 when the length is in inches instead. Thickness is always in inches even when the length is in feet, which is the trap that catches most people. So an 8/4 board 7-1/2 in wide and 8 ft long is (2.0000 x 7.5 x 8) / 12 = 10.00 board feet.
Hardwood thickness is counted in quarter inches before planing. Surfacing takes 3/16 in off stock 1-1/2 in and under and 1/4 in off stock 1-3/4 in and over, but the yard bills the rough number either way - so an 8/4 board is charged at 2.0000 in and arrives at 1.7500 in.
| Quarter | Rough (in) | Surfaced S2S (in) | Planed off (in) |
|---|---|---|---|
| 4/4 | 1.0000 | 0.8125 (13/16) | 0.1875 |
| 5/4 | 1.2500 | 1.0625 (1-1/16) | 0.1875 |
| 6/4 | 1.5000 | 1.3125 (1-5/16) | 0.1875 |
| 8/4 | 2.0000 | 1.7500 (1-3/4) | 0.2500 |
| 10/4 | 2.5000 | 2.2500 (2-1/4) | 0.2500 |
| 12/4 | 3.0000 | 2.7500 (2-3/4) | 0.2500 |
| 16/4 | 4.0000 | 3.7500 (3-3/4) | 0.2500 |
Doyle is a formula, ((D - 4)squared / 16) x L, clamped below 4 in; it under-scales small logs heavily and over-scales very large ones. Scribner Decimal C is a published 1846 table, not a formula: the widely quoted approximation returns 40 board feet for a 12 ft by 10 in log where the table says 30, so it is read from the table and a log outside it is reported as outside it. International 1/4 inch takes the log in four-foot sections with 1/2 in of taper per section and is issued in 5 board-foot steps; it is the most accurate of the three.
How to calculate board feet · What 4/4 lumber means · The board foot chart · Log scale rules compared
All Board Foot Calculator₊ guides
Board feet = thickness in inches x width in inches x length in feet, divided by 12. If your length is in inches instead, divide by 144. One board foot is 144 cubic inches, which is a piece 1 in thick, 12 in wide and 12 in long. The trap is that thickness and width stay in inches even when the length is in feet, and that is where most wrong answers come from.
4/4 is the hardwood trade writing thickness in quarters of an inch, so 4/4 is 1 in rough, 5/4 is 1.25 in, 6/4 is 1.5 in and 8/4 is 2 in. Hardwood is billed on the rough thickness, so an 8/4 board is charged at 2.0000 in even though a board surfaced two sides arrives at 1.7500 in. That is how the trade prices lumber rather than a yard shorting you, and it is the most expensive misunderstanding in the category.
Yes. Board Foot Calculator keeps the formula on screen and tappable, and tapping a total expands it line by line with your own inputs echoed back, so you can see exactly where the number came from. Every output carries its unit label as well, so you never read a bare number and have to guess whether it means inches, board feet or money.
Yes. Quarter thicknesses are a picker covering 4/4, 5/4, 6/4, 8/4, 10/4, 12/4 and 16/4, with a rough versus surfaced two sides toggle, so 8/4 reads 2.0000 in rough and 1.7500 in S2S. Every field takes fractions and decimal inches, so 1-1/2 in and 1.5 in are both fine, and there is voice entry when your hands are dirty. Each input is labelled with the trade word plus a plain-English gloss, so THICKNESS also tells you it is the small dimension.
Yes, and it shows all four numbers at the same time: net board feet, waste percent, gross board feet and the cost of each. Net is what your finished parts need and gross is what you actually buy, where gross = net x (1 + waste percent / 100). Woodworkers commonly allow roughly 15 to 20 percent for straightforward work in clear stock and 30 percent or more for rough lumber you have to joint and rip, for figured or knotty boards, and for anything with a lot of short parts.
Saved multi-board projects come with the one-time Shop Unlock. You can name a project, add as many boards as the job takes, and read per-board totals alongside the project total. The free calculator covers one board at a time, as often as you like.
Cut list layout is part of the one-time unlock, and it treats grain direction as a constraint with a manual override for when you want to place a part yourself. A project exports as CSV or PDF with pricing included, or goes out through the standard share sheet.
Yes, with the one-time unlock. The price book is yours to edit per species, per supplier and per thickness, priced per board foot, and it applies automatically while still letting you override the price on any single board. It sorts and searches and is built to stay usable well past a hundred entries. Pricing stays optional throughout: a board with no price still contributes volume and is never quietly counted as zero.
Log scale results come with the one-time unlock and cover all three rules: Doyle, Scribner Decimal C and International 1/4 inch. You enter small-end diameter and the log length, or circumference plus length if you measure with a tape. Scribner is read from the published table rather than approximated, so a size that is off the table is reported as outside the published table instead of guessed at. Logs are scaled on the small end, inside bark.
Everything runs on the phone, with no account, no sign-in, no network call and no ads, so it works at a lumber rack or in a mill yard with no signal. Free and permanent: single-board board-foot math with the working shown, the quarter picker with its rough versus surfaced toggle, fractions and decimals, a pieces field, the full net and waste and gross breakdown, one hand-entered price, species names, the log input form and voice entry. The one-time Shop Unlock is a single purchase and not a subscription, and it adds saved multi-board projects, the cut list, the price book, log scale results, and CSV and PDF export.