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 2020

Sometimes during measured survey work, you often cannot measure elements such as walls due to access and safety issues. Often you only need an approximate measurement and can use photographs to count bricks to get an approximate length.

Using our free online brick length and height calculator you can quickly count the bricks and work out an approximate height or width of a wall. Our calculator allows you to change the brick/block size, mortar gaps etc to get your estimate as accurate as possible.

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.

Stair Calculator Terminology Diagram

Stair Run and Rise Diagram

Stair Calculator

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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 = 42º

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.