Estimate risers, treads, tread depth, stair angle and optional tread cost.
The preferred riser height is used to estimate an initial number of risers.
The total rise is then divided by the selected whole-number riser count to calculate the actual riser height.
The number of treads is one fewer than the number of risers for a simple straight flight.
Available horizontal run is divided by the tread count to calculate the approximate tread depth.
The stair angle is calculated from total rise and total horizontal run.
These dimensions are planning values and are not a substitute for applicable building-code requirements.
A stair layout begins with the total vertical rise and the horizontal run available for the flight. The calculator uses those project dimensions to estimate a practical whole-number riser count, actual riser height, tread count, tread depth and approximate stair angle.
The calculator estimates the number of risers and treads, the actual riser height, tread depth and approximate stair angle from the dimensions entered. If stair width is supplied, it also estimates total tread surface area. An optional price per tread can be used for a simple tread material cost estimate.
The initial riser count is based on total rise divided by preferred riser height, rounded to a whole number with a minimum of two risers. Actual riser height is then total rise divided by that riser count. For a simple straight flight, the calculator uses one fewer tread than risers.
For a total rise of 2.8 m and a preferred riser height of 0.175 m, the calculator gives 16 risers. The actual riser height is therefore 0.175 m. A simple straight flight has 15 treads.
The approximate stair angle from a 2.8 m rise and 4.2 m horizontal run is about 33.7°.
Once the tread count is known, available horizontal run is divided by the number of treads. More available run produces a greater calculated tread depth, while less run produces a smaller tread depth and a steeper overall stair angle.
The calculated dimensions are planning values and should be checked against the dimensional and safety requirements that apply to the actual project.
When stair width is entered, total tread surface area is calculated as the number of treads multiplied by tread depth and stair width.
When a price per tread is supplied, estimated tread cost is the tread count multiplied by that price. Stringers, risers, landings, rails, fixings, labour and other construction costs are not automatically included.
Measure finished floor-to-floor rise carefully and confirm the usable horizontal run before relying on a layout. Allow for finished floor build-ups and verify the actual construction configuration.
Before construction, check riser height, tread depth, headroom, landings, handrails, structural requirements and every relevant dimension against applicable local building codes and professional project requirements.
Use the Stair Calculator as an early planning aid, then verify the proposed stair geometry on site and against applicable construction and safety requirements before purchasing materials or building the stair.