What this calculator does
Stud count is the wall length divided by the spacing, plus one for the closing end, plus extras around every opening. A 6 metre wall at 400 mm centres with one door and one window needs 20 studs.
The openings are where counts go wrong. Each door or window needs a king stud and a jack stud on both sides, so two openings add four studs before any cripples above and below. Counting only the field studs undershoots every time.
The formula
Field studs are the wall length divided by the spacing, rounded up, plus one because a run of bays needs a stud at both ends. Two extra studs are added per opening for the king and jack pair. The count excludes cripple studs above a header and below a sill, and excludes the plates.
| Term | Meaning |
|---|---|
| On-centre spacing | Stud centres, commonly 400 or 600 mm, or 16 and 24 inches. |
| King stud | A full-height stud beside an opening, running plate to plate. |
| Jack or trimmer stud | A shorter stud beside the king, carrying the header. |
| Cripple stud | Short studs above a header or below a sill, not counted here. |
The inputs explained
| Field | What to enter |
|---|---|
| Wall length (m) | Wall length in metres. |
| Stud spacing | On-centre spacing. 400 mm and 600 mm are the metric standards; 16 and 24 inch are the imperial equivalents. |
| Doors | Number of doors. |
| Windows | Number of windows. |
When to use it
Ordering framing timber
The stud count is the main quantity in a stud wall, before plates and noggins.
Comparing stud spacings
Going from 400 to 600 mm centres saves timber but limits what the wall can carry and support.
Planning a partition
A non-loadbearing partition can often use wider spacing than a loadbearing wall.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How does spacing change the stud count?
The same wall at a range of on-centre spacings.
| Stud spacing | Studs needed | Field studs, on-centre | Extra studs for openings (king & jack) |
|---|---|---|---|
| 400 mm centres | 20 | 16 | 4 |
| 600 mm centres | 15 | 11 | 4 |
Questions
Should I use 400 or 600 mm centres?
400 mm for loadbearing walls and anywhere plasterboard needs more support, such as ceilings or walls taking heavy fixings. 600 mm is common for non-loadbearing partitions and saves timber, but thin board can show slight bowing between studs.
How many extra studs does an opening need?
At minimum a king and a jack on each side, so four per opening, of which this counts two. Wider openings may need doubled jacks to carry the header. Cripple studs above and below are additional and depend on the opening height.
Why one more stud than the spacing suggests?
Because a wall of n bays needs n plus one studs, with one at each end. The same logic applies to fence posts. Dividing the length by the spacing gives the bays, not the studs.
Does this include plates and noggins?
No. Top and bottom plates run the wall length and are usually ordered by linear metre. Noggins or blocking between studs are additional again, and the quantity depends on how many rows the design calls for.
For board on the finished frame, see the drywall calculator. For header sizing over openings, see the door header size calculator.