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Stair Steps And Riser Calculator

Work out stair steps and riser instantly with clear inputs, formula shown and shareable results.

About Stair Steps And Riser Calculator

Riser count is the total rise divided by the preferred riser, rounded to a whole number, and the actual riser is then the rise divided by that count — all risers must be equal. Total run is one fewer going than the riser count, and pitch should stay at or below 42 degrees for a domestic stair.

Formula

Stair geometry

risers = round(total rise / preferred riser); actual riser = rise / risers; run = (risers - 1) x going

Worked example

With the default values below, Stair Steps And Riser Calculator returns Number of risers of 15. Change any input above and every figure here is recalculated in your browser.

Inputs used

Total floor-to-floor rise
2,700 mm
Preferred riser height
180 mm
Going (tread depth)
250 mm
Available headroom
2,000 mm

Results

Number of risers
15 risers
Actual riser height
180.00 mm
Total horizontal run
3,500 mm
Pitch angle
35.75 °

Step by step

  1. 1Values used
  2. 2Stair geometry
  3. 3Number of risers= 15 risers
  4. 4Actual riser height= 180.00 mm
  5. 5Total horizontal run= 3,500 mm
  6. 6Pitch angle= 35.75 °

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.

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

Frequently Asked Questions

Why must all risers be equal?

Because people step by feel, not by looking. A single odd riser is the classic trip hazard and is prohibited by building regulations.

What is the 2R + G rule?

Twice the riser plus the going should be between 550 and 700 mm. It captures the comfortable relationship between step height and depth.

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