Staircase Design Calculator

Work out staircase design instantly with clear inputs, formula shown and shareable results.

About Staircase Design Calculator

The number of risers must divide the floor height exactly, so the preferred riser is used only to find the nearest whole count and the actual riser follows from dividing back. There is always one fewer tread than riser. The classic comfort rule is that twice the riser plus the going should fall between 550 and 700 mm.

Formulas

Riser count

Risers = round(floor height / preferred riser); actual riser = floor height / risers

Comfort rule

2 x riser + going should be 550 to 700 mm; total going = (risers - 1) x tread

Worked example

With the default values below, Staircase Design Calculator returns Number of risers of 17. Change any input above and every figure here is recalculated in your browser.

Inputs used

Floor to floor heightminimum 100 mm: 3,000 mm
Preferred riser heightminimum 80 mm: 175 mm
Tread goingminimum 150 mm: 280 mm
Stair widthminimum 500 mm: 1,200 mm

Results

Number of risers: 17
Actual riser height: 176.47 mm
Total going: 4,480 mm
Two risers plus going check: Comfortable — within the 550 to 700 mm range (633 mm, width 1200 mm)

Step by step

1Values used
2Riser count
3Comfort rule
4Number of risers= 17
5Actual riser height= 176.47 mm
6Total going= 4,480 mm
7Two risers plus going check= Comfortable — within the 550 to 700 mm range (633 mm, width 1200 mm)

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Preliminary estimate only. Stair geometry, headroom, handrails and guarding must comply with the building code adopted locally.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Stair geometry, headroom, handrails and guarding must comply with the building code adopted locally.

Frequently Asked Questions

How is the Staircase Design figure worked out?

Risers = round(floor height / preferred riser); actual riser = floor height / risers. The number of risers must divide the floor height exactly, so the preferred riser is used only to find the nearest whole count and the actual riser follows from dividing back.

Can risers vary within a flight?

No. Codes require all risers in a flight to be equal within a few millimetres because an uneven riser is a serious trip hazard, particularly on descent.

What values do I need to enter?

This calculator takes 4 inputs: Floor to floor height, Preferred riser height, Tread going, Stair width. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.