About the Stud Calculator
A framed wall — timber or steel — is a row of vertical studs between a bottom plate and a top plate, with boards fixed to both faces. Framing is how most houses in North America are built, and how internal partitions go up almost everywhere.
The basic count is straightforward: one stud for every spacing along the wall. But the basic count is always short, for three reasons. There is a stud at both ends, so the count is spaces plus one. Corners and junctions need extra studs so boards have something to fix to on each side. And every door and window needs its own studs around it.
This stud calculator handles all of those, and also works out the plates — the bottom plate and the top plate, usually doubled on load-bearing walls — in the stock lengths you can buy.
How to Use the Stud Calculator
Choose imperial (feet and inches) or metric.
Enter the wall length and the stud spacing, measured centre to centre: 16 or 24 inches, or 400 or 600 mm.
Enter the number of corners and wall junctions in the run, and the number of doors and windows.
Choose a double or single top plate, and the stock length you buy plate timber in.
Adjust the waste allowance — 10% is the default.
How the Studs Are Worked Out
grid studs = (wall length ÷ spacing, rounded up) + 1
corner extras = 2 × corners
opening extras = 4 × openings
studs = (grid + extras) × (1 + waste %)
plate length = wall length × 3 (double top plate)Step-by-Step Example
A 20 ft wall at 16 in centres, two corners, one window, double top plate.
Grid: 240 in ÷ 16 = 15 spaces + 1 = 16 studs
Corners: 2 × 2 = 4
Opening: 1 × 4 = 4
Total: 24 × 1.10 = 27 studs
Plates: 3 × 20 ft = 60 ft ÷ 16 ft stock → 5 lengths with wasteSpaces Plus One
As with fence posts and rebar, the stud count starts with the spaces between studs, not the studs themselves. A 20-foot wall at 16 inches has 15 spaces — and 16 studs, because there is one at each end. Forgetting the extra stud is the most common framing undercount. When the length does not divide evenly, the last space is shorter, but it still needs a stud at its end.
Why 16 Inches (and 24, 400 and 600 mm)
Stud spacings are chosen to match board sizes. A standard sheet of drywall or plywood is 48 inches (4 ft) wide, and 16 inches divides into it exactly three times, 24 inches twice. So when studs are on 16 or 24-inch centres, every sheet edge lands in the middle of a stud and can be fixed.
In metric, sheets are 1200 mm wide, and 400 and 600 mm spacings do the same job. A spacing that does not divide the sheet width leaves edges hanging between studs, which need extra framing — noggins or blocking — behind them.
16 inches gives a stiffer wall and is standard for load-bearing walls in the US. 24 inches uses about a third fewer studs and suits many partitions and advanced framing designs, where allowed.
Openings: King, Jack and Cripple Studs
Every door or window opening is framed with:
King studs — full-height studs on each side of the opening.
Jack studs (trimmers) — shorter studs inside the kings that hold up the header, the beam across the top of the opening.
Cripple studs — short studs above the header and below a window sill, which keep the stud rhythm for fixing boards.
The calculator adds four studs per opening for the kings and jacks. It does not remove the grid studs that fall within the opening, because they are cut down to make cripples and the offcuts are rarely enough — which keeps the estimate on the safe side.
Plates
The bottom plate (sole plate) runs along the floor and the top plate along the top of the studs. Load-bearing walls in the US usually have a double top plate, with joints staggered, which ties walls together at corners and spreads loads from above. Non-load-bearing partitions often use a single top plate. Either way, plate timber is bought in long stock lengths, and the calculator counts how many you need.
Timber or Metal Studs
Timber studs are the traditional choice, easy to cut and fix to, and forgiving of small errors. In North America 2×4 and 2×6 are standard; in the UK, 38 × 89 or 47 × 100 mm CLS timber is common for partitions.
Metal studs — light-gauge steel channels — are straight, light, do not warp or rot, and are widely used for commercial partitions. They are cut with snips, fixed with self-tapping screws, and set out on the same 400, 600, 16 or 24-inch spacings, so the same stud count applies.
Whichever you use, keep the material consistent within a wall, and check whether the wall is load-bearing before choosing, as that decides the size and spacing the design requires.
Understanding Your Result
Studs needed is the total including extras and waste.
Breakdown shows the grid studs and the extras for corners and openings.
Plates gives the number of stock lengths and the total plate length.
Worth knowing says whether your spacing suits standard sheet widths.
When Should You Use This Calculator?
Planning a partition wall in a loft, basement or extension.
Estimating timber for a framed extension or shed.
Comparing 16 and 24-inch spacing for timber cost.
Before ordering, to buy plates in suitable stock lengths.
Common Mistakes
Counting spaces, not studs. Add one.
Forgetting corners. Boards need backing on both faces.
Ignoring openings. Each needs king and jack studs.
Choosing a spacing that does not suit the boards. Stick to 16, 24, 400 or 600.
Buying plates to the exact length. Joints and offcuts need allowance.