Plan a staircase: number of steps, riser height, tread run, angle and stringer length.
Divide the total rise by the maximum riser height and round up to get the number of steps. A 108 in (9 ft) rise with a 7.75 in limit needs 14 risers of 7.71 in, 13 treads, and a 10 in tread gives a 37.6° angle.
The Stair Calculator works out the dimensions of a straight staircase from the total rise (floor-to-floor height) and the tread run. It returns the number of steps, the exact riser height, total run, stair angle and the nose-to-nose stringer length, and checks the layout against common residential limits and comfort rules.
You can let it choose the number of steps from a maximum riser height, aim for a target riser, or fix the number of steps; the run can be entered per step or as the total run. Add tread thickness to find the shorter first riser. Always confirm dimensions with your local building code. To estimate material areas, see the Square Footage Calculator.
A staircase is built from equal risers and treads; there is always one more riser than tread, because the top floor acts as the last tread.
| Input | Steps | Riser | Tread | Angle | Stringer |
|---|---|---|---|---|---|
| 108 in (9 ft) rise, 10 in tread | 14 | 7.71 in | 10 in | 37.65° | 169.01 in |
| 9 ft rise, 11 in tread | 14 | 7.71 in | 11 in | 35.04° | 179.2 in |
| 3 m rise, 28 cm tread, 19 cm max riser | 16 | 7.38 in | 11.02 in | 33.81° | 203.2 in |
| 108 in rise, 15 steps, 10 in tread | 15 | 7.2 in | 10 in | 35.75° | 176.82 in |
Rise is the height of one step; run (tread) is its depth; nosing is the overhang of the tread over the riser; headroom is the clear height above the stairs; the stringer is the sloped structural member that carries the treads. Limits vary by location; typical residential values are below.
| Item | Typical limit |
|---|---|
| Maximum riser height | 7.75 in (19.7 cm) |
| Minimum tread depth | 10 in (25.4 cm) |
| Minimum stair width | 36 in (91.4 cm) |
| Minimum headroom | 6 ft 8 in (203 cm) |
| Handrail height | 34–38 in (86–96.5 cm) |
| Guard height (rise over 30 in) | at least 34 in (86 cm) |
| Nosing | 0.75–1.25 in (1.9–3.2 cm) |
Tape measures use sixteenths of an inch; use this chart to convert measurements for the calculator.
| Fraction | Decimal (in) | Millimetres |
|---|---|---|
| 1/16 | 0.0625 | 1.6 |
| 2/16 | 0.1250 | 3.2 |
| 3/16 | 0.1875 | 4.8 |
| 4/16 | 0.2500 | 6.3 |
| 5/16 | 0.3125 | 7.9 |
| 6/16 | 0.3750 | 9.5 |
| 7/16 | 0.4375 | 11.1 |
| 8/16 | 0.5000 | 12.7 |
| 9/16 | 0.5625 | 14.3 |
| 10/16 | 0.6250 | 15.9 |
| 11/16 | 0.6875 | 17.5 |
| 12/16 | 0.7500 | 19.0 |
| 13/16 | 0.8125 | 20.6 |
| 14/16 | 0.8750 | 22.2 |
| 15/16 | 0.9375 | 23.8 |
| 16/16 | 1.0000 | 25.4 |
Divide the total rise by the maximum riser height (7.75 in in many codes) and round up. 108 in ÷ 7.75 = 13.9, so 14 risers.
Divide the total rise by the number of risers. 108 in ÷ 14 = 7.71 in.
One fewer than the number of risers, because the upper floor forms the final step.
A riser of about 7 in (17.8 cm) and a tread of about 11 in (28 cm) is comfortable; 2 × riser + tread should be 24–25 in.
Most residential stairs are 30°–37°. Above about 42° they feel steep and are generally not suitable for a main residential staircase.
Use the Pythagorean theorem on the total rise and total run. This is the straight nose-to-nose length; cut stringers need extra length for the notches and end cuts.
The horizontal distance covered by the treads: tread depth × number of treads. It does not include the top landing.
The bottom riser is cut shorter by the thickness of the tread so every step feels the same.
Many residential codes allow up to 7.75 in (19.7 cm), but check your local code — some regions allow 8.25 in or 190 mm.
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