Length over spacing, plus one
Studs sit at a fixed spacing measured center to center, so counting them is division. Convert the wall to inches, divide by the spacing, round up, and add one stud to cap the far end. This is the field count — corners and openings are added on top.
A 20 ft wall at 16″ on center: 240 ÷ 16 = 15, plus 1 = 16 studs. Always round up — rounding down leaves a gap with no framing.
16″ vs 24″ on center
Wider spacing means fewer studs and less lumber, but code only allows 24″ on center for non-bearing walls. Load-bearing 2x4 walls stay at 16″.
Going to 24″ spacing drops the stud count by roughly a third and cuts lumber about 25% — but it is reserved for non-load-bearing partitions.
Beyond the field studs
- Corners. Add 3 studs at each corner for a traditional corner, or 2 for an advanced-framing corner.
- Top and bottom plates. Top plate is doubled (2 × length), bottom plate is single (1 × length). Order 5–10% extra for cut waste.
- Doors. Each opening adds 2 king studs and 2 jack studs, minus the field studs the opening removes — usually about 1 extra stud net for a 36″ door.
- Windows. Same as a door plus cripple studs above the header and below the sill, so about 8 studs before subtracting the field studs it displaces.
- Nominal is not actual. A 2x4 measures 1.5″ × 3.5″, and a 2x6 is 1.5″ × 5.5″ — use the actual size when laying out wall thickness.
Common questions
How many studs do I need for a wall?
Multiply the wall length in feet by 12, divide by the spacing in inches, round up, then add 1 for the stud at the far end. A 20 ft wall at 16 inches on center needs (240 divided by 16) plus 1, which is 16 studs before corners and openings.
What is the difference between 16 and 24 inch on center?
Spacing on center is the distance from the middle of one stud to the middle of the next. 16 inch spacing is the standard for load-bearing walls; 24 inch is allowed on non-bearing walls and uses about 25 percent less lumber but is less stiff.
How much top and bottom plate do I need?
The top plate is doubled, so it is twice the wall length; the bottom plate is single, so one times the wall length. A 20 ft wall needs 40 ft of top plate and 20 ft of bottom plate, plus 5 to 10 percent for waste.
