Enter your total rise and get the full cut sheet — riser height, tread run, stringer length, angle, and code checks — with a scaled drawing of your stairs.
📑 What each term means — click to expand diagrams
Riser = vertical face of one step. Tread / run = horizontal depth of one step. Stringer length = the diagonal cut board, by Pythagoras from total rise and total run.
Floor opening is the hole cut in the upper floor, measured back from the wall. The ceiling stays solid everywhere else — headroom is the clearance at the opening's near edge (the "header"), which is always the tightest point on the stairs.
Standard mount drops the stringer so a solid triangular base sits under the steps — simple to build, needs a bottom "drop cut". Flush mount notches the board so it stays an even thickness all the way along — a cleaner look, but a trickier cut.
Only total rise is required — pick any unit per field. "Auto" picks the fewest risers under your max height; or choose a custom count / target riser height from the dropdown.
How it was solved
History
| # | Total rise | Risers | Riser ht | Tread | Total run | Stringer | Angle |
|---|
No calculations yet. Your results will be saved here in this browser.
How stair stringers work
The vocabulary in 30 seconds
A stringer is the sawtooth-cut board (usually a 2×12) that carries the steps. Each notch has a vertical riser cut and a horizontal tread (run) cut. The total rise is the finished-floor-to-finished-floor height; the total run is how far the staircase reaches horizontally. A staircase with n risers has n − 1 treads, because the top landing itself acts as the final tread.
The math, start to finish
- Count the risers: divide total rise by your maximum riser height and round up.
n = ceil(rise ÷ max riser). Rounding up is what keeps every riser under the limit. - Actual riser height:
riser = rise ÷ n— this spreads the height perfectly evenly, which matters because uneven risers are the #1 cause of stair trips. - Total run:
(n − 1) × tread depth. - Stringer length: Pythagoras.
√(rise² + run²), then buy the next standard board size with some waste allowance. - Angle:
atan(rise ÷ run)— comfortable stairs land between roughly 30° and 38°.
The comfort rule: 2R + T
Carpenters have used this since the 1600s (it's attributed to the French architect Blondel): twice the riser plus the tread should land around 24–25 inches (610–635 mm) — the span of a natural human stride on a slope.
Tall risers with deep treads make you lunge; short risers with shallow treads make you mince. Trading riser against tread while keeping 2R+T constant is how you tune a staircase to feel right. This calculator scores your combination automatically.
"Drop the stringer" — the classic first-step mistake
When you install treads on top of the cut stringer, every step gains one tread-thickness of height — except it all cancels out between steps. The two places it doesn't cancel: the bottom step becomes one tread-thickness too tall, and the top step too short.
The fix is to cut the bottom of the stringer down by exactly the tread thickness ("dropping" it) before installation. This calculator prints the exact first-riser cut height for you in the worked steps. Skip this and your staircase will fail the riser-uniformity code check — and feel wrong on the very first step.
Code limits used here — and an important caveat
The defaults follow the widely used IRC residential values: maximum riser 7¾" (196 mm), minimum tread depth 10" (254 mm), and riser uniformity within 3/8" across the flight. Many regions differ (commercial stairs, decks, and countries using other codes have their own numbers), and rules also exist for headroom, width, handrails, and guards that this calculator does not check.
Always verify against your local building code before cutting. This tool is a planning aid, not a substitute for your local inspector's requirements.
A worked example
Deck stairs with a 45" total rise, 10½" treads, 7¾" max riser:
- Risers: ceil(45 ÷ 7.75) = 6.
- Riser height: 45 ÷ 6 = 7½" — under the max ✓
- Treads: 6 − 1 = 5; total run = 5 × 10.5 = 52½".
- Stringer: √(45² + 52.5²) ≈ 69⅛" → buy an 8 ft 2×12.
- Comfort: 2(7.5) + 10.5 = 25.5 — right at the edge of the ideal band.
- Drop the stringer by 1" (tread thickness): first riser cut = 6½".