How Many Studs Do I Need?

Studs are bays plus one

That's the whole thing, and it's the mistake almost everyone makes on their first wall.

Divide the wall by the spacing and you get the number of bays — the gaps between studs. But a wall needs a stud at both ends as well as between each pair. One bay needs two studs. Two bays need three.

Order one stud per bay and you're exactly one short, every wall, every time.

The arithmetic

A 20-foot wall at 16 inches on centre.

Convert to inches, because the spacing is in inches:

20 × 12 = 240 inches

Divide by the spacing to get bays:

240 ÷ 16 = 15 bays

Add one:

15 + 1 = 16 studs

Plate timber is three times the wall length — one bottom plate, and a doubled top plate:

20 × 3 = 60 linear feet

What "on centre" means

The spacing is measured from the centre of one stud to the centre of the next, not from edge to edge.

That's not pedantry — it's what makes sheet materials work. Drywall, plywood and OSB come in 4-foot widths, and 48 divides evenly by both 16 and 24. So a sheet's edge lands on the middle of a stud, leaving half of it for the next sheet to fix to.

Measure edge to edge and every sheet joint falls in mid-air.

16 or 24 inches?

16 is the standard, and nearly everything else is designed around it — insulation batts, sheet goods, fixing schedules.

24 saves timber and is used on some non-load-bearing walls. The trade-offs are real: the wall is springier, and drywall is noticeably more prone to sagging or showing waves between studs, especially on a ceiling.

If the wall carries load, this isn't a preference. What's required is set locally and worth checking rather than choosing.

What this count leaves out

The stud count is the easy part. The extras add up fast:

• Every door and window needs king studs, jack studs, a header and cripples above and below. How many depends on the opening's width and what the wall carries.
• Every corner and wall intersection takes two or three extra studs depending on the method.
• Blocking wherever cabinets, handrails, a TV bracket or grab rails will be fixed. Put it in now — nobody enjoys finding out afterwards.

None of those are in the number above. Count them per opening and per corner and add them.

Order extra, and sight them first

Timber is not straight. It arrives bowed, twisted, cupped, occasionally split — and a stud with a crown in it telegraphs through the finished wall under raking light.

So buy a few more than the count. Sight down every stud before it goes up — hold one end at eye level and look along it — and set the worst aside for short cripples above and below openings, where a bend doesn't matter.

Ten minutes of sorting is the difference between a flat wall and one you notice every time the afternoon sun hits it.

Where people go wrong

• Bays instead of bays + 1. The one at the top of this article.
• Measuring edge to edge. Spacing is centre to centre, or every sheet joint misses.
• Forgetting the plates. Three times the wall length on a load-bearing wall, twice on a partition with a single top plate.
• Counting only the studs. Openings and corners are a real chunk of the order.
• Ordering exactly. Some of what arrives won't be usable.
• Skipping the blocking. Free to add while the wall is open, a nightmare afterwards.

The short version

Wall length in inches ÷ spacing = bays. Studs = bays + 1. Plate timber = length × 3. Spacing is centre to centre so sheet edges land on studs. Add framing for every opening and corner separately, order a few extra, and sight each one before it goes up.