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Woodworking calculators
Small, honest tools for the arithmetic that ruins boards. Each one runs entirely in your browser, needs no signup, and every result can be linked, printed and shared.
mm ⇄ inch fractions
Instant both ways, snapped to 1/8–1/64 with the rounding error shown in millimetres. With a printable workshop card.
Open →Wood movement calculator
Width, species and your indoor humidity swing in — seasonal expansion in millimetres out, with the gaps and slotted holes to build in.
Open →Shelf sag calculator
Span, thickness, wood and load in — sag now and after years of creep out, judged against the visibility threshold. If it fails, you get the fix.
Open →Board foot calculator
Thickness in sawmill quarters, width, length and price in — board feet and cost out, with the metric equivalent.
Open →Cut list calculator
Parts in, optimised boards out — with the saw kerf subtracted for every cut. Shows each board to scale, in cutting order.
Open →Why these exist
Every one of these tools covers a sum that looks too small to get wrong and ruins wood when it is: the kerf that eats a shelf, the width that ignored the dados. They are free because the arithmetic should be. The bigger thing being built here — sketch in, dimensioned plan and cut list out — is over on the main page.