Stair Calculator

What Is a Stair Calculator?

A stair calculator is a tool for working out the basic dimensions of a staircase from the available floor-to-floor height, number of risers and tread depth. It can calculate the individual rise of each step, total horizontal stair run, number of treads and approximate stair angle.

Stair dimensions are important when planning a staircase because the vertical rise, horizontal tread and overall run determine how much space the staircase requires and how steep it will be. This calculator provides quick geometric calculations for initial planning and estimation.

Why Use a Stair Calculator?

Calculating staircase dimensions manually requires several related calculations. This tool provides the principal measurements together so you can quickly assess a proposed straight staircase configuration.

How to Use the Stair Calculator

Measure the vertical distance between the finished lower and upper floors, then enter your proposed staircase dimensions into the calculator.

1. Enter the floor-to-floor height — Enter the total vertical distance between the two finished floor levels.
2. Select the measurement unit — Choose millimetres, centimetres, metres, inches or feet.
3. Enter the number of risers — Enter the number of vertical rises planned for the staircase.
4. Enter the tread depth and calculate — Enter the horizontal depth of each tread and select "Calculate Stairs" to see the resulting staircase dimensions.

How to Calculate Stair Rise and Run

The first measurement needed for a staircase calculation is the total floor-to-floor height. This is divided by the number of risers to determine the individual riser height. For example, if the floor-to-floor height is 2,800 mm and the staircase has 16 risers, each riser is 175 mm high.

The horizontal run is determined from the tread depth and number of treads. In a conventional straight staircase where the upper floor forms the final landing, a staircase with 16 risers generally has 15 treads. With a 250 mm tread depth, the horizontal stair run would therefore be 3,750 mm.

Understanding Stair Riser Height

The riser is the vertical component of a step. Consistent riser heights are important because variations can create a trip hazard and make a staircase difficult to use. The calculated riser height should therefore be checked against the requirements that apply to the particular building and staircase.

Understanding Tread Depth

The tread is the horizontal surface of a step on which the foot is placed. Tread depth affects both the amount of horizontal space required by a staircase and its overall angle. Increasing the tread depth generally increases the total stair run when the number of treads remains unchanged.

Stair Dimensions and Building Regulations

The calculator provides geometric results for planning and estimation. Staircases are subject to building regulations and design requirements that can vary according to location, building type and intended use. Requirements can apply to riser height, going or tread depth, pitch, headroom, width, landings, handrails, guarding and other features.

The number of risers should be selected so that the resulting individual riser height is appropriate for the intended staircase and complies with the applicable requirements. A mathematically valid result is not necessarily a legally compliant staircase.

The total stair run calculated by this tool does not include additional space that may be required for landings or other staircase components. It also does not calculate structural stringer dimensions, headroom or detailed construction cuts.

Always verify the final staircase design against the building regulations and technical requirements applicable to your project before construction.

Frequently Asked Questions