Staircase Calculator

The one thing a staircase must not have is a step that is a different height from the others — that is what people trip on, and it is what happens when the height is divided by hand and each riser rounded. Give the floor-to-floor height and this divides it into a whole number of identical risers, works out a going that suits them, and shows the flights one and two steps either side so you can see what you are trading.

Floor to floor, in millimetres

Finished floor to finished floor, not floor to ceiling.

Run available, in millimetres

How far the flight may reach. 0 if there is no constraint.

What kind of stair

Riser height to aim at, in millimetres

Between 100 and 250. Around 190 is a comfortable domestic step.

14 risers of 185.7mm, 13 treads with a going of 228.6mm

The flight reaches 2971.4mm along the floor at a pitch of 39.1 degrees.

Risers	Riser	Going	Run	Pitch	2R + G
12	216.7mm	220mm	2420mm	44.6°	653.3mm
13	200mm	220mm	2640mm	42.3°	620mm
14	185.7mm	228.6mm	2971.4mm	39.1°	600mm
15	173.3mm	253.3mm	3546.7mm	34.4°	600mm
16	162.5mm	275mm	4125mm	30.6°	600mm

✓ Every riser is identical, and they add back to the height — 14 risers of 185.7mm makes 2600mm — the height you gave
✓ There is one fewer tread than there are risers — 14 risers and 13 treads, because the top step is the landing
✓ The pitch matches the rise and going it is built from — 39.1 degrees, from 185.7mm over 228.6mm
✓ Within the figures usually quoted for a private — a home stair — riser under 220mm, going over 220mm, pitch under 42 degrees
✓ Twice the rise plus the going lands where it should — 2R + G is 600mm, against the 550 to 700mm this rule of thumb calls comfortable

What this generator does

Tries every whole number of risers that keeps the step within the quoted limit, chooses a going from the 2R + G rule, and reports the riser height as an exact division of the height rather than a rounded figure.

How to use this tool

Measure finished floor to finished floor and type it in millimetres.
Say how much run the flight may take, or leave it at zero if there is no constraint.
Choose what kind of stair it is, which sets the figures to compare against.
Read the number of risers, the riser height, the going and the pitch.

Understanding the controls

Floor to floor, in millimetres: The total climb, measured from the finished surface of one floor to the finished surface of the next — not floor to ceiling, which leaves out the thickness of the upper floor.
Run available, in millimetres: How far the flight may reach along the lower floor. Set it and the going is trimmed to fit; leave it at zero and the going follows the comfort rule instead.
What kind of stair: Which set of figures to compare against: a private stair in a home, a utility stair in a workplace, or a general access stair used by the public. Each has a different maximum riser, minimum going and maximum pitch.
Riser height to aim at, in millimetres: Your preference, used to choose between the flights that work. Around 190 is a comfortable domestic step; lower is gentler and takes more room.

Common use cases

Sketching a loft or extension staircase before drawing it properly
Checking whether a flight will fit the run available
Working out how many treads to order
Seeing what one more or one fewer riser does to the pitch
Understanding why a flight feels steep by looking at 2R + G

How this generator works

The height is divided by a whole number of risers and kept as an exact fraction, never rounded — the check multiplies the riser height back by the count and demands the original height to within a tenth of a millimetre, which is what guarantees no step is taller than its neighbours. The going comes from the rule that twice the rise plus the going should land near 600mm, held to the minimum for the kind of stair and trimmed to the run available. Pitch is recomputed from the rise and going that are actually reported, so the angle cannot drift away from the numbers beside it.

Randomness and fairness

Nothing is random. The same height and settings always give the same flight.

For how randomness is produced across the whole site, see how Generate Random works.

Limitations and good to know

The figures quoted for each kind of stair are the commonly cited ones; a real staircase is signed off against the regulations in force where it is built, which this is not a substitute for.
Winders, landings and tapered treads are not planned here — this is a straight flight.
Headroom is not checked, and it is the constraint that most often decides a loft staircase.
Nosing overhang, tread thickness and the floor finish all shift the numbers a few millimetres.

Privacy and your data

The arithmetic runs in your browser. No measurements are transmitted or stored.