Stud Calculator
Work out how many wall studs and how much plate lumber you need for a straight wall.
Studs to buy
18
- Studs before extra
- 16
- Plate lumber (3 plates)
- 60.0 ft
A 20 ft wall at 16 in on center needs 16 studs. With 10% extra, buy 18.
Calculation breakdown
| Step | Formula | Result |
|---|---|---|
| Spaces along the wall | 20 ft × 12 ÷ 16 in | 15 |
| Studs | 15 rounded up, + 1 for the end | 16 |
| Studs with extra | 16 × (1 + 10%), rounded up | 18 |
| Plate lumber | 3 × 20 ft (bottom plate + double top plate) | 60.00 ft |
How it works
Enter the length of one straight wall and pick the stud spacing. The extra for waste (10%) and an optional price per stud are in the advanced options.
Worked example
A 20 ft wall at 16 in on center with 10% extra, at $4.25 a stud:
- Spaces: 20 × 12 ÷ 16 = 15
- Studs: 15 + 1 = 16
- With 10% extra: 16 × 1.1 = 17.6, rounded up to 18 studs
- Plates: 3 × 20 ft = 60 ft
- Cost: 18 × $4.25 = $76.50
Sources
Frequently asked questions
How many studs do I need for a wall?
Divide the wall length in inches by the stud spacing, round up, and add one stud for the end. A 20 ft wall at 16 in on center is 240 ÷ 16 = 15 spaces, so it needs 16 studs before any extra.
Should studs be 16 or 24 inches on center?
Both are common. The building code table for wood stud walls (IRC Table R602.3(5)) sets the maximum spacing by stud size, grade and what the wall carries, and lower-grade 2×4 studs cannot go wider than 16 in. Check your local code before choosing 24 in.
Does this include corners, doors and windows?
No. The count is for a plain straight wall. Corners, wall intersections and openings need extra studs, such as king and jack studs beside a door or window, so add those on top or raise the extra percentage.
How many plates does a wall need?
A typical bearing wall has one bottom plate and a double top plate, so three plates in total. The calculator multiplies the wall length by 3 to give the plate lumber.
How do I calculate studs in metric?
Metric framing usually uses 400 mm or 600 mm spacing. A 6 m wall at 400 mm is 6,000 ÷ 400 = 15 spaces, so 16 studs.
Results are estimates for planning only. Stud size, grade and spacing must meet your local building code.