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Board foot calculator
Thickness in the quarters the sawmill speaks, width, length and your price — board feet per piece, for the stack, and what the stack costs before you're standing at the counter doing it in your head.
Your boards
A board foot is 1 in × 12 in × 1 ft of rough lumber — thickness × width × length ÷ 12 with inches and feet.
The tally
Board feet per piece, for the stack, and the cost appear here.
Board feet from https://sketchmethis.com/board-feet — free, no signup.
How board feet work
A board foot is a volume: 1 in thick × 12 in wide × 1 ft long. The formula is thickness (in) × width (in) × length (ft) ÷ 12. An 8/4 board 6 in wide and 8 ft long is 2 × 6 × 8 ÷ 12 = 8 bd ft — at $6.50 a foot, $52 before you've built anything.
Two conventions to know at the counter. Thickness is quoted in quarters of an inch — 4/4 ("four-quarter") is 1 in, 8/4 is 2 in — and it means the rough-sawn thickness: surfaced 4/4 stock measures about 13/16 in, but you pay for the full quarter. Anything thinner than 4/4 is also billed as 4/4, because it was milled from it; this calculator rounds up the same way.
Sanity numbers
| Board | bd ft |
|---|---|
| 4/4 × 6 in × 8 ft | 4 |
| 4/4 × 8 in × 8 ft | 5.33 |
| 8/4 × 6 in × 8 ft | 8 |
| 8/4 × 10 in × 10 ft | 16.67 |
| 12/4 × 12 in × 12 ft | 36 |
Rule of thumb for the lumberyard walk: a 4/4 board carries width-in-inches × length-in-feet ÷ 12 board feet — a 6-incher gives you half a board foot per foot of length.
Questions
Do I measure the rough or the surfaced size?
Price is charged on the rough size the board was sawn to — the quarters. Your project needs the surfaced size. Buy by quarters, design by what's left after the planer: 4/4 → roughly 13/16 in, 8/4 → roughly 1¾ in.
How much extra should I buy?
The usual planning allowance is 15–30% over the cut list — defects, grain matching, mistakes, and the ends you cut off because they're checked. Softwood from the home centre: less. Figured hardwood: more.
Metric supplier?
One board foot is 0.00236 m³ (about 2.36 litres); a cubic metre is roughly 424 board feet. The result line shows your total in m³ — or use the metric version of this calculator.
The tally is easy. Knowing what to buy is the hard part.
Board feet price the stack — but which boards, at which lengths, with which cuts? Sketch Me This is a tool being built to answer that end of it: sketch or describe the piece, get dimensioned drawings and the full cut list, ready to take to the lumberyard.