Stair Rise and Run Explained
Rise and run are the two numbers that make a staircase safe, legal and comfortable to climb. Here is what they mean, how to calculate them, and the limits you must stay within.
By the Calculate My Reno Team / Published
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Every staircase comes down to two measurements: rise (the vertical) and run (the horizontal). Get the ratio right and the stairs feel natural; get it wrong and they feel steep, shallow or unsafe.
The terms
- Total rise: the full vertical height, floor to floor.
- Unit rise (riser): the height of one step.
- Total run: how far the staircase travels horizontally.
- Unit run (going / tread depth): the depth of one step you stand on.
- Number of risers / treads: there is always one more riser than tread.
How to work out the steps
- Measure the total rise (finished floor to finished floor).
- Divide by a comfortable riser height - around 175–190 mm (7–7.5 in) - and round to a whole number. That is your number of risers.
- Divide the total rise by that number of risers for the exact riser height.
- Choose a tread depth within code, and multiply by the number of treads for the total run.
The stair calculator does all of this and draws the staircase, so you can see the rise, run and any landing before you cut anything.
The comfort rule
Generations of builders use a simple relationship to make stairs feel right:
2 × riser + tread ≈ 600–640 mm (about 24–25 in)
Stay near this and the steps match a natural stride. Tall risers with shallow treads feel steep; short risers with deep treads feel like a slog.
The code limits (check yours)
| Limit | US (typical IRC) | UK (typical) |
|---|---|---|
| Max riser | ~7.75 in | ~220 mm |
| Min tread / going | ~10 in | ~220 mm |
| Max pitch | ~37–42° | ~42° |
These vary by jurisdiction and there are extra rules for handrails, headroom and landings, so always confirm your local building code before building.
Next
Once you have your rise and run, you cut the stringers to match - see how to cut stair stringers. Building outdoor steps? See how to build deck stairs.
Frequently asked questions
What is the difference between rise and run on stairs?
Rise is the vertical part - the "total rise" is the full floor-to-floor height, and the "unit rise" (riser height) is the height of each step. Run is the horizontal part - the "going" or unit run is the depth of each tread, and the "total run" is how far the staircase travels horizontally. Together they set the steepness of the stairs.
How do I calculate the number of steps?
Divide the total floor-to-floor height by a comfortable riser height (around 175–190 mm / 7–7.5 in) and round to a whole number of risers - that gives the step count. Then divide the total height by that number of risers to get the exact riser height. The stair calculator does this and draws the result.
What are the building-code limits for stairs?
They vary by country, but typical residential limits are: maximum riser around 7.75 in (US) or 220 mm (UK), minimum tread/going around 10 in (US) or 220 mm (UK), and a maximum pitch near 42°. Always check your local building code, as exact figures and handrail rules differ.