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Staircase Calculator: Riser, Tread, Run and Angle

This free staircase calculator works out how many steps a staircase needs from the total height. It gives the exact riser height, a comfortable tread depth, the total run, the angle and the length of the stringer.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is It and When Do You Need It?

A staircase must divide the rise into equal steps that are comfortable and legal. Steps that are too steep or uneven are dangerous. The calculation gives the number of steps and the exact riser.

Enter the total rise and a preferred riser.

How to Use This Tool

  1. Enter the total rise in millimetres.
  2. Enter your preferred riser height.
  3. Optionally enter a preferred tread depth.
  4. Press Calculate.

How the Calculation Works

Steps = total rise ÷ preferred riser, rounded to the nearest whole number. The exact riser is total rise ÷ steps. If you give no tread, it is chosen as 630 − 2 × riser. The run is (steps − 1) × tread. The stringer is √(rise² + run²), and the angle is arctan(rise ÷ run).

Worked Example

A total rise of 2,700 mm with a preferred riser of 175 mm gives 15 steps of 180 mm. With a 270 mm tread, the run is 3,780 mm, the angle 35.5° and the stringer 4,645 mm.

Common Uses

  • House and loft stairs.
  • Decks and garden steps.
  • Planning space for a staircase.
  • Checking a design against comfort rules.

Tips and Common Mistakes

  • Keep all risers equal within a few millimetres.
  • Check headroom above the stairs.
  • Check your local building rules.

Next, you may need the flooring calculator, gravel and mulch calculator, tire size calculator, AWG wire gauge calculator.

Everything runs in your browser. Nothing you type is uploaded, stored or sent to any outside service.

Frequently Asked Questions

Two risers plus one tread should come to about 600 to 650 mm. A riser of 175 mm suits a tread of about 260 to 300 mm.
Risers are normally 150 to 220 mm, and treads at least 220 to 250 mm. Building codes differ by country, so check yours.
The top step is the floor above, so there is one less tread than risers.
The sloping board that supports the steps. Its length is the diagonal of the rise and the run.

Disclaimer: results are calculated in your browser from the numbers you enter. Check important results before you rely on them for money, health, safety or legal decisions.