Step-height tool
Stair Riser Calculator
Work out riser height, riser count, tread run and pitch from total rise — with equal risers, code checks and a live section diagram. Free, no account needed.
Finished floor to finished floor.
7-7.5in is comfortable; risers are equalised.
Horizontal depth, nosing excluded.
Plumb from the nosing line to the ceiling above.
Landings, stringers & handrail
Half-landings or quarter-turns in this flight.
16in suits most treads; 12in for thin or composite.
Measured above the nosing line.
4in (100mm) sphere rule.
Sets the bottom stringer drop.
Your flight
15 risers × 7.33in
14 treads at 10.50in / 26.7cm · 36.8 degree pitch
- Riser height (equal)
- 7.33in / 18.6cm
- Tread run (going)
- 10.50in / 26.7cm
- Total run
- 147.00in / 373.4cm
- Cut line (diagonal)
- 183.60in / 466.3cm
- Stringer stock length
- 195.60in / 496.8cm (16.3ft)
- Pitch
- 36.8 degrees
- 2R + G
- 25.17in / 63.9cm
- Stringers
- 4 at 12.0in centres (65.2ft stock)
- Handrail length
- 207.60in / 527.3cm (17.3ft)
- Balusters
- 39 at 5.2in centres
Code & comfort checks
IRC (US) allows a maximum 7.75in riser. Every riser in a flight must match within 3/8in.
Minimum going is 10.00in. Shallow treads are the single biggest cause of descending falls.
Comfortable domestic flights sit between 30 and 37 degrees; 42 degrees is the absolute ceiling.
Two risers plus one going should land between 24in and 25in (600-640mm) for a natural stride.
IRC (US) expects at least 36.0in of clear width above the handrail height.
Minimum headroom is 80in measured plumb from the tread nosing line.
IRC wants a graspable handrail 34-38in above the nosing line, continuous for the full flight, and no gap that passes a 4in sphere.
Guidance only — confirm against your local building control before you cut or pour.
Compare riser counts
| Risers | Riser | Going | Run | Pitch |
|---|---|---|---|---|
| 14 | 7.86in | 10.50in | 11.4ft | 38.9° |
| 15 | 7.33in | 10.50in | 12.3ft | 36.8° |
| 16 | 6.88in | 10.50in | 13.1ft | 34.9° |
The highlighted row is your current flight. Nudging the riser count is usually the cheapest way to bring a steep or shallow stair back inside code.
Advanced layout
Mark-out schedule, framing deductions & take-off
Quick answer
How do you calculate stair riser height?
A stair riser is the vertical face of a single step. To calculate riser height, divide the total rise (finished floor to finished floor) by a whole number of risers, choosing that number so the result sits between roughly 7in and 7.75in for US residential stairs, or under 220mm for UK private stairs. Every riser in the flight must come out identical — round the riser count first, then divide back into the total rise, rather than picking a riser height and hoping the last step matches.
- Riser = the vertical board or open gap at the front of one step.
- Riser height = total rise divided by the rounded number of risers.
- US residential maximum riser is commonly 7 3/4in under the IRC.
- UK private-stair maximum riser is commonly 220mm under Document K.
- Riser height must match within about 3/8in (10mm) across the flight.
- Riser count is always one more than tread count when the top floor is the last step.
What a riser is, and what it is not
A riser is one vertical step face, not the whole flight. People searching for a 'stair height calculator' are usually asking one of two different questions: how tall is a single step (riser height), or how tall is the whole staircase (total rise). This calculator answers both from a single measurement, but it is worth being precise about which figure you are quoting to a supplier or an inspector — a spec that says '7in riser' means every step is 7in tall, not that the whole flight is 7in.
| Total rise | Target riser | Riser count | Actual riser height | Notes |
|---|---|---|---|---|
| 70in / 1778mm | 7.00in | 10 | 7.00in | Exact fit, no rounding needed |
| 90in / 2286mm | 7.25in | 12 | 7.50in | Rounded up from 12.4 |
| 98in / 2489mm | 7.50in | 13 | 7.54in | Rounded from 13.1 |
| 115in / 2921mm | 7.25in | 16 | 7.19in | Rounded from 15.9 |
| 150in / 3810mm | 7.40in | 20 | 7.50in | Rounded from 20.3 |
Know your numbers in 30 seconds
Enter your step count, tread depth and riser height — the stair runner calculator gives you the exact length to order, in metres and feet, with waste included.
Open the stair runner calculatorRounding the riser count is the whole trick
Almost nobody's total rise divides evenly by a nice round riser height, which is exactly why the calculation works backwards from a whole number of risers rather than forwards from a target height. Pick the riser count that lands nearest your comfort target, then let the height fall out of the division. This is the step people skip when they build a flight by eye, and it is why so many older staircases have one slightly-off step near the top or bottom.
- Never split a remainder into just the top or bottom step — spread it evenly by recalculating the riser height for the whole flight.
- A riser height under roughly 4in usually means you actually need a ramp, not a step.
- A riser over 7 3/4in (IRC) or 220mm (UK Document K) fails code even if only the top or bottom step is out.
- Open-riser stairs still have a riser height for code purposes — it is the vertical gap, and most codes limit how large a sphere can pass through it for child safety.
Riser height, comfort and the 2R + G rule
Riser height alone does not determine comfort — it works together with the tread going. The 2R + G rule (two riser heights plus one going, targeting 24-25in) is a quick sanity check: a 7.5in riser needs roughly a 9.5-10in going to feel right, while a shallow 6in riser wants a deeper 12-13in going. If your riser height is fixed by a tight floor-to-floor height, use this rule to size the going rather than defaulting to a 10in minimum that might feel cramped.
Measuring an existing riser to match new stairs
To match an existing flight, measure from the top of one tread to the top of the tread above at the same point on the nosing, not to the floor at the bottom of the riser board — the two can differ by the thickness of the flooring finish and throw a matching flight out by a fraction of an inch.
From riser height to finished stairs
Once the riser height and count are locked in, they drive the tread run, the pitch and — for a finished flight — the runner length. The home page's stair runner calculator and stair runner length calculator both take riser height, going and nosing as inputs and return the exact carpet length, so it is worth confirming your risers here first. If the risers came out uneven on an existing staircase, the stair rise and run calculator can help you work out where the error is before you order materials.
Whatever you decide, get the numbers first: the stair runner calculator doubles as a stair runner length calculator, adding nosing wrap, landings, winders, pattern repeat and waste so you order the right length the first time.
Frequently asked questions
What is a stair riser exactly?
The riser is the vertical piece — solid board, open gap, or poured concrete face — between the back of one tread and the front edge of the tread above it. It sets the step height. An 'open riser' stair skips the board entirely but the vertical rise between treads is still measured and still has to meet the same height limits.
How do I calculate stair riser height from total rise?
Divide total rise by a target riser (commonly 7 to 7.5in) and round to the nearest whole number to fix the riser count, then divide the total rise by that count so every riser comes out equal. For a 98in rise: 98 / 7.25 = 13.5, round to 14 risers, then 98 / 14 = 7.0in per riser exactly.
What is the standard or maximum stair riser height?
The IRC caps residential risers at 7 3/4in with no minimum, though most comfortable stairs use 7 to 7.5in. UK Approved Document K caps private-stair risers at 220mm (about 8.66in) and common stairs in flats at 190mm. Commercial codes (IBC) are typically stricter, often capping risers around 7in.
How many risers do I need for a given rise?
Riser count is the total rise divided by a target riser height, rounded to the nearest whole number — always round rather than truncate, and recompute the riser height afterward so nothing is left over. A 132in rise at a 7.25in target gives 18.2, rounds to 18 risers at 7.33in each.
Why do stair risers have to be equal?
The body memorises a rhythm after the first two or three steps and stops watching the floor. A riser that is even 3/8in taller or shorter than the rest breaks that rhythm and is one of the most common causes of stair falls, which is exactly why codes set a tight tolerance rather than leaving it to feel.
How is riser height different from riser count or total rise?
Total rise is the whole flight's vertical climb. Riser count is how many individual steps that climb is divided into. Riser height is the result of dividing one by the other. Mixing these terms up in a spec ('7in rise' meaning riser height versus total rise) is a common source of ordering mistakes for stringers and risers alike.
What riser height should a concrete or exterior step use?
Exterior concrete steps are often built shallower than interior stairs — a 6 to 7in riser with an 11 to 12in tread is common for comfort in the wet, and some jurisdictions cap exterior risers lower than interior ones. Check the concrete stair calculator for slab thickness and volume once the riser height is set.
Is the riser calculator free to use?
Yes, the riser count, riser height, tread count, run, pitch and code checks are all free with no account. A free account adds the step-by-step mark-out schedule that lists the exact height of every riser from the finished floor, useful when snapping lines on a stringer.
Related tools & guides
Start with the numbers: our stair runner calculator also works as a stair runner length calculator, adding nosing wrap, landings, winders, pattern repeat and waste so you order the right length first time.