Free tool
Stair Calculator
Enter your total rise and tread depth — get the riser count, exact riser height, number of treads, total run, and stringer length. Free, no signup for the estimate.
Stair layout
0 risers
- Riser height (actual)0 in
- Treads0
- Total run0 in
- Stringer length0 in
- Estimated cost—
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Or download it now (PDF)How to calculate a staircase
A staircase comes down to one measurement — the total rise — and dividing it into equal steps that land within code. Get the riser count right and everything else, tread count, run, and stringer length, follows from it. Nail it once on paper and you cut clean stringers instead of guessing on the saw.
1. Measure the total rise
Measure straight up from the finished lower floor to the finished upper floor. That total rise is the number every step is carved out of — measure to the finished surfaces, not the subfloor, so your riser heights come out even once flooring is down.
2. Solve for the riser count
Divide the total rise by a comfortable riser height (around 7–7.75 in) and round to a whole number — you can’t build a fractional step. Then divide the total rise by that count to get the exact riser height. The calculator does this and keeps every riser identical, which is what code wants.
3. Count treads and total run
There is always one fewer tread than risers because the top landing is the last step. Multiply the tread count by your tread depth to get the total run — the horizontal distance the stair covers, which tells you if it fits the opening.
4. Size the stringer
The stringer is the diagonal, so its length is √(rise² + run²). The calculator returns it so you can buy stock long enough to lay out and cut every notch with a little to spare.
Measuring the job is step one. Turning it into a priced, professional quote is faster inside CrewRivet. See the deck calculator, the framing calculator, or the job pricing calculator.
Stair calculator FAQ
- How do I calculate stairs?
- Start with the total rise — the finished-floor-to-finished-floor height. Divide it by a comfortable riser height (around 7–7.75 in) and round to a whole number of risers. Divide the total rise by that count to get the exact riser height, then subtract one to get the number of treads. Multiply the treads by your tread depth for the total run. This calculator does all of that the moment you enter your total rise.
- What is a comfortable riser height?
- Most codes cap risers around 7.75 in and want them all within about 3/8 in of each other. Seven inches is the classic comfortable target. Because the riser count must be a whole number, the calculator solves for the exact riser height that divides your total rise evenly — enter your preferred riser and it finds the count that lands closest.
- How long does a stair stringer need to be?
- The stringer is the diagonal, so its length is the hypotenuse of the total rise and total run: √(rise² + run²). The calculator shows this stringer length so you can pick stock long enough to cut all your notches with material to spare.
- Why is there one fewer tread than risers?
- The top landing acts as the last "step," so a flight always has one more riser than it has treads. If you have 14 risers you cut 13 treads. Getting this off by one is the most common stair mistake — the calculator handles it for you.
- Is the calculator free?
- Yes — the live estimate is free with no email required. Enter your email only if you want the free Job Pricing Kit (pricing worksheet, markup cheat-sheet, and invoice + quote templates) sent to your inbox.