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
Skip to the tool
Open the Stair Calculator
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, because the top floor itself acts as the last “step” - you climb the final riser and step straight onto the landing, with no separate tread board there.
How to actually measure the total rise
Everything else comes from this one number, so measure it carefully. You want the vertical drop from the lower floor to the upper floor - not the diagonal, and not the height of the stairwell opening.
- Find the finished-floor levels. “Finished floor” is the surface you will actually walk on once the job is done (the tiles, boards or carpet), not the bare subfloor. If the flooring is not down yet at one or both levels, add its thickness in - get this wrong and every step ends up slightly off.
- Measure straight up, dead vertical. Stand a long spirit level or a straight batten plumb (truly upright) at the edge of the upper floor and run your tape from the lower finished floor up to the top of the upper finished floor. A plumb bob or a level laid against the tape keeps it from leaning, which would read long.
- Measure at both sides. Take the rise at the left and the right of where the stairs will sit. Floors are rarely perfectly level, and even a 10 mm difference changes the step layout. If the two readings differ, use the larger one and shim or scribe the stringer to suit.
- Working from a rough opening? If the upper floor is still just joists with no flooring, measure to the top of the joist and add the finished floor thickness on top. Note it on your sketch so you do not forget it later.
Write this total rise down - it is the number you feed into every step that follows.
How to work out the steps
- Take your total rise from above.
- 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. This 600–640 mm sweet spot sits inside the wider 550–700 mm (about 22–27.5 in) range that the UK and Australian codes allow, so aim for the middle and you are both comfortable and within code.
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.