Stair Stringer Calculator
Enter the total vertical rise (finished floor to finished floor) and get the full stair layout: how many risers, riser height, treads, total run, and how long to cut your stringers.
Runs entirely in your browser — your numbers never leave this page.
How it works
Stair layout starts from one rule: keep every riser the same height. The calculator divides your total rise into equal risers near the comfortable 7-inch target:
Risers = round(Total rise ÷ 7) → Riser height = Total rise ÷ Risers
Total run = (Risers − 1) × Tread depth
Stringer length = √(Rise² + Run²)
- Example: 36 in rise → 5 risers × 7.2 in, 4 treads × 11 in = 44 in run, stringer ≈ 56.9 in.
- Top tread: the upper floor itself is the last "tread," so there is always one fewer tread than risers.
- Stringer length is the hypotenuse — buy a board longer than this (2×12 lumber) and lay out the steps with a framing square.
- Uniformity matters: code requires all risers in a flight to be within 3/8 in of each other — uneven steps trip people.
Frequently asked questions
What is the maximum riser height allowed by code?
The International Residential Code (IRC) caps risers at 7-3/4 inches and requires treads at least 10 inches deep. Every riser in a flight must be within 3/8 in of the others. Local codes may be stricter — always check.
What is the most comfortable riser and tread combination?
The classic 7/11 rule: 7-inch risers with 11-inch treads. It matches a natural stride and is what most residential stairs are built to. Steeper than 7.5 in starts feeling like a ladder.
How many stringers do I need?
Space cut stringers no more than 16 inches on center — so a 36-inch-wide stair needs 3 stringers. Wider stairs or heavy use may need more. Solid (un-notched) stringers can span a bit further.
Cut stringers vs. solid stringers — which is better?
Cut (notched) stringers are easier: you saw the stair profile into a 2×12 and the treads sit on the notches. Solid stringers are stronger (no wood removed) with treads housed in routed grooves or cleats — better for wide or heavy-duty stairs, but more work.
What is stair nosing, and how much overhang do I need?
Nosing is the rounded front edge of the tread that overhangs the riser below. Code requires a nosing projection of 3/4 in to 1-1/4 in on treads under 11 in deep — it gives your foot more landing area.
How much headroom do stairs need?
The IRC requires 6 ft 8 in of headroom minimum, measured vertically from the nosing line. This is the number-one thing DIY basement stairs get wrong — check it before you cut.
Do I measure rise from subfloor or finished floor?
Always finished floor to finished floor. If flooring is not installed yet, add its thickness to your measurement — a 3/4 in hardwood floor changes every riser height if you forget it.
Do stairs need a landing?
The IRC limits a single flight to 12 feet of vertical rise before a landing is required. Landings must be at least as wide as the stair and 36 in deep in the direction of travel.
What is the difference between tread depth and "going"?
Tread depth is the full board including the nosing overhang; going is the horizontal distance between nosings (tread depth minus nosing). An 11 in tread with 1 in nosing has a 10 in going — which is the code minimum.
Can I use 2×10 lumber for stringers?
It is risky. After cutting notches, a 2×10 leaves very little wood at the throat of each cut — the weak point. 2×12 is the standard for cut stringers; it leaves enough meat below the notches to carry the load safely.