Framing a wall and not sure how many studs to buy? The math is simple once you know the spacing. This guide gives you the formula, explains what else you need beyond the studs themselves, and works through common examples.
The quick formula
Number of studs = (wall length in inches ÷ stud spacing) + 1
Stud spacing is measured “on center” (OC), meaning from the center of one stud to the center of the next. The two common spacings are 16 inches OC and 24 inches OC. The +1 accounts for the stud at the start of the wall.
A handy shortcut for 16 inch spacing: you need roughly one stud per linear foot of wall. An 8 foot wall takes 7 to 8 studs, a 12 foot wall takes 10 to 11.
16 inch vs 24 inch spacing
16 inch on center is the default for most walls. It lines up with 4×8 sheet goods (drywall, plywood, OSB), so sheet edges land on a stud. Use 16 inch OC for load-bearing walls, exterior walls, and anywhere you will hang heavy cabinets or a TV.
24 inch on center saves lumber and is common for non-load-bearing interior partition walls and some garage walls, where codes allow it. Check your local building department before using 24 inch spacing on anything structural.
What the formula does not include
The formula counts only the vertical studs in the middle of the wall. A real wall needs more lumber:
- Plates. Every wall needs a bottom (sole) plate and two top plates. That is 3 boards the same length as the wall. For a 12 foot wall, buy plates as 12 foot boards or splice shorter ones.
- Corners. Where two walls meet, add one extra stud per corner so there is solid wood to nail drywall into on both sides.
- Intersections. Where an interior wall ties into another wall, add a stud (or a pair) for drywall backing.
- Door and window openings. Each opening needs 2 king studs (full height, one each side) and 2 jack studs (shorter, supporting the header), plus a header across the top and cripple studs above and below.
Worked examples
8 foot wall at 16 inch OC
8 feet = 96 inches. 96 ÷ 16 = 6 spaces, plus the starting stud = 7 studs. Add 3 plates and 1 extra stud for each corner. If the wall has a door, add 2 king and 2 jack studs. Total for a plain 8 foot wall with one corner: about 8 studs plus 3 plates.
12 foot wall at 16 inch OC
12 feet = 144 inches. 144 ÷ 16 = 9 spaces, plus 1 = 10 studs. With one corner and one door opening: 10 + 1 corner + 4 for the door = about 15 studs, plus 3 plates.
Same 12 foot wall at 24 inch OC
144 ÷ 24 = 6 spaces, plus 1 = 7 studs. Same wall, about 30 percent less lumber, where 24 inch spacing is allowed.
Framing a whole 12×12 room
Four walls of 12 feet is 48 linear feet. At 16 inch OC that is 48 ÷ (16 ÷ 12) = 36 stud spaces. Add 4 starting studs (one per wall) and 4 extra studs for the four corners: about 44 studs. One door adds 4 more. Plates: 48 linear feet × 3 = 144 feet of plate lumber, or 12 boards of 12 feet.
Buy extra for waste
Add about 10 to 15 percent to your stud count. Some boards arrive bowed, twisted or split, and you will make at least one bad cut. For the 44 stud room above, buy 48 to 50.
Common stud choices are 2×4 for interior walls and 2×6 for exterior walls that need thicker insulation. Buy studs in the actual wall height you need: an 8 foot ceiling typically uses 92-5/8 inch precut studs, which with three plates gives a finished wall height of 97-1/8 inches, ready for drywall.
Related calculators and guides
- Drywall calculator – sheets for your new walls and ceiling
- How many sheets of drywall do I need for a room
- Insulation calculator – batts for 16 or 24 inch stud bays
- Square footage calculator – measure the room first
- Board foot calculator – for hardwood and specialty lumber
Estimates only. This is general guidance, not professional advice. Confirm details with your supplier, installer or local building department.