Metric Unit Calculator
Construction calculator

Stair Calculator

Number of risers: -
Calculation explained

How this result was calculated

The formula, your substituted values, and the evaluated result are shown below.

This is a planning estimate. Confirm dimensions, allowances, material specifications, applicable codes, and supplier requirements before purchasing or construction.
Recommended resources

Products that may help

Recommended

Udemy Education

Udemy is an AI-powered skills acceleration platform transforming how companies and individuals across the world build the capabilities needed to thrive in a rapidly evolving workplace.

View offerAffiliate link — we may earn a commission at no extra cost to you.

How the Stair Calculator works

Estimate the number of stair risers.

Before using the result

This is a planning estimate. Confirm dimensions, allowances, material specifications, applicable codes, and supplier requirements before purchasing or construction.

Keep exploring
AC Tonnage CalculatorEstimate air-conditioning capacity from floor area and design load.Air Changes per Hour CalculatorCalculate air changes per hour from airflow and room volume.Air Conditioner BTU CalculatorEstimate air-conditioner capacity.Aluminum Weight CalculatorEstimate aluminum sheet or plate weight using a standard density.Angle Cut CalculatorCalculate an equal angle cut for a symmetric joint.Angle of Depression CalculatorCalculate angle of depression.

About this calculator

Estimate the number of stair risers.

Calculator guide

How the stair calculator works

The first decision in any staircase is how many steps (risers) you need to climb the total height. This calculator divides the total rise by the riser height you are aiming for:

Number of risers = total rise (mm) ÷ target riser height (mm)

The total rise is measured from finished floor to finished floor, so include floor coverings like tiles or timber on both levels. The answer will rarely be a whole number. Round up, then divide the total rise by that whole number to get your actual riser height.

Worked example: a 2,700 mm floor-to-floor height

  1. Target riser 175 mm: 2,700 ÷ 175 = 15.43
  2. Round up to 16 risers
  3. Actual riser: 2,700 ÷ 16 = 168.75 mm
  4. A straight flight has one fewer tread (going) than risers, so this one has 15 treads
  5. Choose a going of 270 mm: total run = 15 × 270 = 4,050 mm

Check it against the rules

Stairs are regulated because small inconsistencies cause falls. In Australia, the National Construction Code (NCC) sets limits for stairs in houses. Current requirements include:

CheckNCC limit (Class 1 dwellings)Example
Riser (R)115 – 190 mm168.75 mm ✓
Going (G)240 – 355 mm270 mm ✓
Slope relationship 2R + G550 – 700 mm607.5 mm ✓

All risers and goings in a flight must be the same (within a small tolerance), and there are also rules for openings, balustrades and handrails. Confirm the current NCC edition and any state variations with your certifier. In the USA, the IRC generally limits residential risers to 7¾" (about 197 mm) with a minimum 10" (254 mm) tread depth.

Common mistakes

Frequently asked questions

What is a comfortable riser height?

Most people find about 165–180 mm with a 250–280 mm going comfortable for a home staircase.

How much floor space does a staircase need?

Multiply the number of treads by the going. For the example, that is about 4.05 m of run, plus landings at the top and bottom.

Do outdoor steps follow the same rules?

Generally yes, if they form part of a required path of travel. External stairs also need slip-resistant treads. Check with your certifier.

Written by Sam Alex, civil engineer. About the author