Stair Calculator: Rise, Run & Tread Count

Calculate the geometry of one straight stair flight from a finished total rise, your chosen number of equal risers, and a horizontal going per tread. The upper landing is the final walking surface: separate treads = risers - 1.

Straight stair rise, run, and tread count

Measurement unitsFinished total rise (in)Number of risers (whole number)Horizontal going per tread (in)Available horizontal tread run (optional) (in)

Measure from the finished lower level to the finished upper landing. A riser is a vertical increment; a tread is a separate walking surface below the landing. This model always uses one fewer separate tread than risers. It does not model an extra tread flush with the upper landing or multiple flights.

Going is the horizontal spacing between successive tread reference points, not the full board depth including its nosing. Enter all length values in the selected unit. For example, 7 ft = 84 in. Changing units clears lengths, while keeping the riser count.

Choose the riser count and going using the applicable project requirements; no code-compliant values are assumed. The available-run comparison covers tread run only, not landing dimensions, door clearance, headroom, or structural space.

Enable JavaScript to calculate. Equal riser height = total rise / number of risers. Separate treads = risers - 1. Total horizontal tread run = separate treads x going. Repeated-step pitch = arctangent(riser height / going).

How are stair rise and run calculated?

Divide the finished total rise by the chosen number of risers. When the upper landing serves as the final walking surface, the number of separate treads is one less than the number of risers. Multiply that tread count by the horizontal going to find the total tread run.

Worked example

A finished total rise of 84 inches divided into 12 equal risers gives a riser height of 7 inches. With the upper landing as the final surface, there are 11 separate treads. A chosen going of 10 inches gives a horizontal tread run of 110 inches. The repeated-step pitch is arctangent(7 / 10), approximately 34.992 degrees. These inputs illustrate the arithmetic and are not a recommended or approved stair specification.

Why not divide total rise by total tread run for the pitch?

The total rise includes one more vertical increment than the number of separate tread goings in this landing convention. The slope between corresponding points on successive treads uses one riser height divided by one going. The diagonal joining the bottom and top endpoints describes different reference points, so it is not used here as the repeated-step pitch.

Can I use the result as a stringer length?

No. A stringer's physical length and cuts depend on top and bottom attachment, bearing, tread thickness, nosing, and reference points. Neither a step-pitch angle nor a total-rise diagonal specifies the finished piece. Use an appropriate detailed layout and product or professional guidance for those requirements.

What if the flight does not fit?

The optional run field shows the arithmetic difference between available tread run and calculated tread run. It does not declare the staircase safe or compliant. Changing the riser count also changes riser height, and changing going affects the run and pitch. Check each revised choice against the full project requirements, including landings and headroom.

What does this model exclude?

This is one straight flight with equal risers. It does not handle winders, spiral stairs, intermediate landings, uneven existing steps, or material quantities. It does not choose stringer spacing, lumber size, fasteners, load capacity, guards, or handrails. Local requirements and the actual finished assembly must be checked separately.

Stair geometry guide

How to calculate stair rise, run and tread count with a worked example and the upper-landing convention explained.