Stair geometry tool
Stair Rise and Run Calculator
Work out riser height, tread run, total run, stair pitch and the diagonal cut line from total rise — with standard rise-and-run ratios by code and a live section diagram.
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
What is stair rise and run and how do you calculate it?
Rise is the total vertical height a flight climbs, measured finished floor to finished floor; run is the total horizontal distance it covers, measured from the face of the first riser to the face of the last. Standard residential rise and run is a 7in to 7.75in riser paired with a 10in to 11in tread run, giving a pitch of roughly 34 to 37 degrees. Divide total rise by a target riser height, round to a whole number, then work the run back from that count of treads.
- Rise = vertical height of the whole flight, floor to floor.
- Run = horizontal distance covered by all the treads combined.
- Riser height = total rise divided by the rounded riser count.
- Tread run = total run divided by the tread count.
- Standard US rise and run: 7-7.75in riser with a 10-11in run.
- Pitch = atan(rise / run); most comfortable flights sit at 34-37 degrees.
Rise and run are whole-flight measurements
Total rise is the vertical distance from one finished floor to the next — not to the subfloor, and not to the top of the joists, but to the surface someone will actually stand on once flooring is laid. Total run is the horizontal distance the flight covers, measured from the leading edge of the bottom riser to the leading edge of the top riser. Get either one wrong by half an inch and the error compounds across every step in the flight.
The two numbers are related but not interchangeable with riser height and tread run, which describe a single step. A stair with 14 risers and a 110in total rise has a riser height of 7.86in per step; the same flight with 13 treads and a 136.5in total run has a 10.5in tread run per step. Keeping the whole-flight and per-step language straight avoids ordering the wrong lumber or the wrong length of stair runner carpet.
| Total rise | Riser count | Riser height | Total run | Tread run | Pitch |
|---|---|---|---|---|---|
| 84in / 2134mm | 12 | 7.00in | 110in | 10.00in | 35.2 deg |
| 98in / 2489mm | 14 | 7.00in | 128.7in | 9.90in | 35.3 deg |
| 112in / 2845mm | 15 | 7.47in | 147in | 10.50in | 35.5 deg |
| 126in / 3200mm | 17 | 7.41in | 168in | 10.50in | 35.2 deg |
| 140in / 3556mm | 19 | 7.37in | 189in | 10.50in | 35.1 deg |
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 calculatorWorked example: from a tape measure to a diagram
Say you measure a floor-to-floor rise of 108in. Target a 7.25in riser: 108 / 7.25 = 14.9, round to 15 risers. Recalculate: 108 / 15 = 7.2in per riser, an easy figure inside the 7-7.75in code envelope. With the top step flush to the upper floor, that flight has 14 treads. Pick a 10.5in run: total run = 14 x 10.5 = 147in. Pitch is atan(108 / 147) = 36.3 degrees, comfortably inside the 30-37 degree comfort band and under the 42-degree UK maximum.
Standard rise and run tables by code
- IRC (US residential): maximum 7 3/4in riser, minimum 10in run, maximum 3/8in variance between steps.
- IBC (US commercial, generally more conservative): typically a 7in maximum riser with an 11in minimum run, though check the adopted local amendment.
- UK Approved Document K (private stair): maximum 220mm rise, minimum 220mm going, maximum 42-degree pitch.
- UK Approved Document K (common stair in flats): maximum 190mm rise, minimum 250mm going.
- These figures are commonly cited maximums and minimums rather than a substitute for checking your local adopted code before construction.
Rise-and-run mistakes worth avoiding
The two errors that show up again and again: measuring rise to the subfloor instead of the finished floor, and forgetting that a run figure quoted for 'the flight' means the total, not the per-tread depth. Both are easy to catch by sanity-checking against the table above before cutting anything.
From geometry to material
Once rise and run are settled, they drive everything downstream: stringer length, the number of deck stair calculator style framing deductions, and — for finished stairs — the amount of carpet needed. The home page's stair runner calculator turns the same riser height, going and nosing figures into an exact runner length in metres and feet, so it is worth running both calculators from the same measurements. If you would rather build the flight from scratch, the stair calculator adds diagonal cut lines and full code checks, and the how to measure stairs for a runner guide walks through capturing rise and run with nothing but a tape and a level.
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 the standard stair rise and run?
In the US, the IRC allows a maximum 7 3/4in riser with a minimum 10in tread run, though most comfortable staircases use a 7 to 7.25in riser with a 10.5 to 11in run. In the UK, Approved Document K measures going instead of run and sets a 220mm minimum on private stairs, with rise capped so the pitch stays under 42 degrees.
What is the difference between rise, run and going?
Rise and run describe the whole flight — total vertical height and total horizontal distance. Riser height and going (the UK term for tread run) describe a single step. Confusing the two is the most common measuring mistake: a 'run' of 140in for a flight is not the same as a '10in run' per tread, and mixing them up throws every downstream calculation off.
How do you work out rise and run from a total staircase length?
If you already know the horizontal space available, divide it by your riser count minus one (for a flush top step) to get the run per tread, then check that figure against the 10in code minimum. This calculator has a 'fit into a fixed opening' toggle that does exactly this and flags treads that come out too shallow.
What rise-to-run ratio feels the most comfortable to walk?
The classic 2R + G rule says two riser heights plus one going should total 24-25in (610-635mm). A 7.25in riser with 10.5in going gives 25in and reads as comfortable. Ratios that satisfy code minimums but land outside 24-25in — a 7.75in riser with a 9in run, say — often feel steeper than the numbers suggest.
How do I convert stair rise and run between inches and millimetres?
Multiply inches by 25.4 for millimetres, or divide millimetres by 25.4 for inches. A common US 7.5in riser is 190.5mm; a common UK 190mm riser is 7.48in. Small rounding differences matter less on their own than keeping every riser in a flight identical, so pick one unit and stay in it for the whole calculation.
Can rise and run be different for every step in a flight?
No — code requires every riser in a flight to match within 3/8in (about 10mm) and every going to match within the same tolerance. A flight that starts at 7in and creeps to 7.5in by the top step is a trip hazard even though each individual riser might be legal on its own.
What stair rise and run do I need for a loft conversion?
Loft stairs are usually rise-constrained by the floor-to-floor height and run-constrained by the landing footprint, which often forces a steeper flight than a main staircase. UK Building Regulations allow a steeper 42-degree 'private stair' pitch for this case, sometimes combined with alternating tread stairs where the run genuinely will not fit otherwise.
Does this calculator show rise and run on a diagram?
Yes. Enter the total rise and either a target riser or the available run, and the live section diagram redraws with the riser height, tread run, pitch and diagonal cut line labelled. Free to use, with no account required for the geometry and diagram.
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.