Studs are counted from the layout, not the wall area: one every 16 or 24 in, plus one to close the run, plus whatever corners and openings need.
Stud calculator
Enter the wall length and spacing, and the extra studs your layout needs.
Enter your numbers to see the result.
How it works
Studs = wall length in inches / spacing, rounded up, plus 1. A 20 ft wall at 16 in on center is 240 / 16 = 15, plus 1 = 16 studs, before extras.
Plates are the horizontal boards at the bottom and top of the wall: one bottom plate and usually a double top plate, so 3 times the wall length.
The extras
Every corner, window and door adds studs: corner posts, king and jack studs, cripples and blocking. How many depends on your framing plan, so the calculator gives you one box to add them, instead of guessing.
Spacing
16 in on center is the most common for walls. 24 in spacing uses fewer studs and is allowed for many walls under the IRC, but it depends on the load, stud size and wall height. Your plans decide.
Frequently asked questions
How many studs for a 10 ft wall?
At 16 in on center, 120 / 16 = 7.5, rounded up to 8, plus 1 = 9 studs before corners and openings.
Why add one stud?
Spacing counts the gaps; you need one more stud than gaps to close the run.
How long are wall studs?
Precut studs for 8 ft walls are commonly 92-5/8 in, which allows for a single bottom and double top plate.