Counting things along a run looks like division. It isn't — there's always one more than you think, and that off-by-one is why people come back from the yard a piece short.
For stud walls, floor joists, ceiling joists and battens. Enter the run and the spacing — we count positions, not divisions.
Works in metric and US imperial — you choose at the start and can switch at any time. Every figure this calculator uses is published with its source, and the result comes with a printable order sheet. No account, no email, and nothing you type leaves your browser.
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Counting things along a run looks like division, and it is not — there is always one more position than there are gaps. A 3.6 m wall at 400 mm centres has nine gaps and ten studs. That off-by-one is why people come back from the yard a piece short, and it is the single thing this page exists to get right.
That is why 400 and 450 mm exist, and why 16 and 24 in exist in the US: they divide neatly into standard board widths. Set out from the wrong end and every board joint falls in mid-air, which means either cutting every sheet or adding timber afterwards. Check the run at both ends too — rooms are rarely square, so measure top and bottom and work from the larger figure.
Plates are separate: top and bottom plates run the full length of the wall, and a doubled top plate is standard in most load-bearing walls. Measure those as running length rather than as pieces. Noggins and blocking are separate too — roughly one row per wall, plus extra wherever a rail, a TV bracket or a board edge needs something to fix to. Order a few extra pieces as well, because timber warps, splits and arrives bowed, and the rejects make noggins.
Divide the run by the spacing and add one — you are counting positions, not gaps. A 3.6 m wall at 400 mm centres needs ten studs, not nine. Then add pieces for openings, and order a few spare because some timber will be rejected.
Because those spacings divide into standard board widths, so plasterboard and sheet material land on a stud. The US equivalents are 16 and 24 inches. Set out from the correct end so the joints fall where the timber is.
No. Plates run the full length of the wall, and load-bearing walls usually have a doubled top plate, so measure them as running length rather than counting pieces.
For the quantity, yes. For the specification, no — sizes, spacing and lintels for structural work come from an engineer or your building code. This counts what the drawing specifies; it does not decide it.