How this stair stringer cut sheet works
The generator divides your total rise into equal risers, adds steps until the height clears the code maximum, and lays the result out as the drawing above:
riser = total rise ÷ risers · treads = risers − 1 · stringer = √(rise² + run²)
At the defaults — a 45 in total rise, 10 in treads, a 7 in target — that is 6 risers at 7 1/2″, 5 treads at 10″, a 4′-2″ total run, and a 5′-7 1/4″ stringer at 42.0° cut from an 8 ft 2×12, with the bottom dropped to 6 1/2″ for 1 in treads. Print it, clamp your stair gauges to the square settings, and step it off.
What each line on the cut sheet means
- Square settings: riser height on the framing square’s tongue, tread run on the blade — the two numbers stair gauges clamp to.
- Risers × height: how many times you step the square down the board, and the plumb height of each notch.
- Bottom drop cut: the first riser is cut one tread-thickness short so every finished step lands equal — the most-skipped cut in stairbuilding.
- Stringer & angle: the point-to-point length (your board check) and the slope for saw bevels.
- The badges: IRC R311.7.5’s 7¾ in max riser and 10 in min tread, checked live.
From sheet to sawdust
- Gauge the square: clamp stair gauges at the tongue/blade settings so every step-off is identical.
- Step it off: trace the notch at each step down the 2×12, keeping the square’s heel tight to the edge.
- Don’t overcut: stop the circular saw at the inside corners and finish with a handsaw — overcuts halve the stringer’s strength.
- Cut the drop last: take the tread thickness off the bottom level cut, then test-fit before cutting its siblings.
- Pattern the rest: the first good stringer is the template — trace, don’t re-measure.
Two habits separate clean flights from creaky ones. Sight down every 2×12 and lay out with the crown up, so the stringer settles flat under load instead of humping a tread. And before you cut stringers two and three, stand the pattern in place against the ledger and the landing — a test-fit catches a mis-measured total rise while it is still one board’s worth of mistake, not three. The stair calculator prices the lumber once the layout checks out.
Stringer layouts by total rise
Common total rises at a 10 in run and 7 in target riser, straight from the engine — deck heights at the top, a full 9 ft floor-to-floor at the bottom:
| Total rise | Risers × height | Stringer | 2×12 board |
|---|---|---|---|
| 36 in | 5 × 7 3/16″ | 4′-5 13/16″ | 8 ft |
| 45 in | 6 × 7 1/2″ | 5′-7 1/4″ | 8 ft |
| 54 in | 8 × 6 3/4″ | 7′-4 7/16″ | 8 ft |
| 63 in | 9 × 7″ | 8′-5 13/16″ | 10 ft |
| 72 in | 10 × 7 3/16″ | 9′-7 1/4″ | 10 ft |
| 108 in | 15 × 7 3/16″ | 14′-8 13/16″ | 16 ft |
Worked example: a 45 in deck stair
The default sheet, derived line by line — 45 in total rise, 10 in treads, 7 in target riser, 1 in tread stock:
treads = 5 × 10″ → total run = 4′-2″
stringer = √(45² + 50²) = 5′-7 1/4″ at 42.0° → an 8 ft 2×12
drop = 7 1/2 − 1 = 6 1/2″ bottom riser cut
Note what the target riser did: 45 ÷ 7 suggests six and a half steps, and the generator settles on six taller-but-legal risers rather than seven shallow ones. If you’d rather have the gentler flight, drop the target to 6.5 and it re-lays the sheet with 7 risers at 6 7/16″ — the stringer gets longer, the climb gets easier, and the sheet stays printable either way.
What this cut sheet doesn’t decide
- Stringer count and span. Three at 36 in wide is common practice; the tread material and span govern.
- Attachment. Hangers, ledger connection and the landing footing are their own details.
- Guards and handrails. Required alongside most flights — the baluster calculator spaces the infill.
- Landings and headroom. Flight length, landing size and 6′-8″ headroom come from the plan, not the stringer.
- Finished-floor differences. Different finishes top and bottom shift the first and last riser — adjust the rise before cutting.
Stringer layout FAQ
How do you lay out a stair stringer?
With a framing square and a pair of stair gauges: clamp the gauges at the riser height on the tongue and the tread run on the blade, then step the square down the 2×12 once per riser, tracing the notch each time. Cut the top plumb line, the notches, and finally the bottom level line minus the drop. This generator prints those exact square settings.
What is the stringer "drop" and why does it matter?
The bottom of the stringer is cut down by one tread thickness. Once treads are installed, every step gains that thickness — except the first, which starts from the floor. Skip the drop and the bottom step is one tread thicker than the rest, which violates the code’s 3/8 in variation rule and is exactly the kind of step people trip on.
How many stringers do stairs need?
Common practice is three stringers for a 36 in wide stair — one each side and one centered — with the tread material’s span rating deciding whether you can stretch to two on a narrow run. Cut one stringer, test-fit it against the deck or floor, and use it as the pattern for the rest.
What size board do stair stringers use?
A 2×12. The notches remove roughly half the board, and the strength of the stringer lives in the uncut wood below them — a common rule keeps at least about 5 in of solid throat. A 2×10 rarely leaves enough; when the sheet shows a stringer past 20 ft it is engineered-beam territory, not sawn lumber.
What is the maximum stair riser height?
Under IRC R311.7.5, risers may be at most 7¾ in and treads at least 10 in deep, and the tallest and shortest riser in a flight may differ by no more than 3/8 in. The generator divides your total rise into equal risers and adds steps until the height passes, then badges both checks on the sheet.
What angle should stairs be?
Most comfortable stairs land between about 32° and 42°. The default sheet — 7½ in risers on a 10 in run — comes out at 42.0°, the steep end of normal. A longer 11 in run at a 7 in riser flattens the flight toward 32°; the angle on the sheet is also your circular-saw bevel reference for the top and bottom cuts.
Do I measure total rise from finished floor to finished floor?
Yes — finished surface to finished surface, not framing to framing. If the two floors will get different finish thicknesses (tile below, hardwood above), add or subtract the difference before you cut, because the code measures riser variation on the finished stair. It is the single most common stringer-layout mistake.
Sources and standards
- IRC R311.7.5: riser max 7¾ in, tread min 10 in, and the 3/8 in max variation within a flight.
- Framing-square practice: rise on the tongue, run on the blade, gauges clamped — the trade’s layout method.
- The drop: bottom riser less one tread thickness — standard stringer practice, and what keeps the flight legal.
- The AHJ governs: adopted edition and local amendments rule the built stair — this sheet is the layout, not the permit.