# Stair Calculator To Work Out Run and Rise Lengths, Free Online Tool

## Use our easy calculator to work out the rise and run (going) lengths of straight length stairs.

Article By: Tom Ayre
Last Update: November 2019

Calculating basic stair run and rise measurements are fairly simple, however, sometimes you might want a bit of verification.

Our stair calculator tool takes the overall run and rise of your staircase along with the desired steps and tells you the calculated run and rise of each step.

You can find the calculator below.

### Stair Calculator Terminology

Elevation Angle = Angle of stairs from horizontal in degrees.
O/A Rise Length = Overall vertical distance between floor levels.
O/A Run Length = Overall horizontal distance between start and end of the stair.
Rise Length = Vertical distance between the stair and next stair.
Run / Going = Horizontal distance from the end of the previous stair and start of next.

### Outline Stair Guidance to British Standards

Private Stairs

Min Rise (mm) = 150 mm
Max Rise (mm) = 220 mm
Min Going (mm) = 220 mm
Max Going (mm) = 300 mm

Utility Stairs

Min Rise (mm) = 150 mm
Max Rise (mm) = 190 mm
Min Going (mm) = 250 mm
Max Going (mm) = 400 mm

General Access Stairs

Min Rise (mm) = 150 mm
Max Rise (mm) = 170 mm
Min Going (mm) = 250 mm
Max Going (mm) = 400 mm

Max Elevation Angle = 42ยบ

### Outline Stair Guidance to British Standards

#### Other Requirements:

• For school buildings, the preferred rise is 150 mm and the preferred going is 280 mm.
• For dwellings, for external tapered stairs that are part of the buildings, the going should be a minimum of 280 mm.
• For existing buildings, alternatives may be proposed if the dimensional constraints do not allow these requirements to be followed.
• There are more complex requirements for stepped gangways in assembly buildings, and there may be a conflict between these requirements and sightlines in some buildings with spectator seating.
• Buildings that are not dwellings and common areas in buildings that contain flats should not have an open riser, should have visual contrast to make nosings apparent, and nosings should not protrude by more than 25 mm.
• The minimum headroom should be 2 m.

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