Stair geometry tool
Stair Pitch Calculator
Work out the pitch of a staircase from the rise and going, checked against UK and US limits — with total run, headroom and the 2R+G comfort rule. 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
Step-by-step mark-out
| Step | Height above floor | Run from first riser |
|---|---|---|
| 1 | 7.33in / 18.6cm | 10.50in / 26.7cm |
| 2 | 14.67in / 37.3cm | 21.00in / 53.3cm |
| 3 | 22.00in / 55.9cm | 31.50in / 80.0cm |
| 4 | 29.33in / 74.5cm | 42.00in / 106.7cm |
| 5 | 36.67in / 93.1cm | 52.50in / 133.3cm |
| 6 | 44.00in / 111.8cm | 63.00in / 160.0cm |
| 7 | 51.33in / 130.4cm | 73.50in / 186.7cm |
| 8 | 58.67in / 149.0cm | 84.00in / 213.4cm |
| 9 | 66.00in / 167.6cm | 94.50in / 240.0cm |
| 10 | 73.33in / 186.3cm | 105.00in / 266.7cm |
| 11 | 80.67in / 204.9cm | 115.50in / 293.4cm |
| 12 | 88.00in / 223.5cm | 126.00in / 320.0cm |
| 13 | 95.33in / 242.1cm | 136.50in / 346.7cm |
| 14 | 102.67in / 260.8cm | 147.00in / 373.4cm |
Deduct one tread thickness so the first riser matches the rest.
Taken off the top of the stringer when the top tread is the finished floor.
Horizontal distance before the ceiling opening clears the nosing line.
Trimmer-to-trimmer opening in the floor above to keep headroom legal.
Includes 12in of extra length per board for the top and bottom cuts.
Board, stone or laminate for the tread faces including nosings.
Paint, stain, carpet or stone coverage for the whole flight.
Includes a 10% waste margin; refine it in the runner calculator.
Like these numbers? Save this flight, attach it to a client project and quote it with a free Riser account.
Continue in Riser — freeQuick answer
How do you calculate the pitch of a staircase?
Stair pitch is the angle of the flight, calculated as arctan(riser height / going). A 7 1/2in riser on a 10in going gives 36.9 degrees. Comfortable domestic stairs sit between 30 and 37 degrees; UK Approved Document K caps a private stair at 42 degrees, and the US IRC effectively caps it near 37.8 degrees through its 7 3/4in riser and 10in tread limits. Anything over 42 degrees is a steep or space-saver stair with its own rules.
- Pitch = arctan(riser / going), measured on the pitch line joining the nosings.
- Comfort band: 30-37 degrees. UK private stair maximum: 42 degrees.
- US IRC limits of 7 3/4in riser and 10in tread give a practical maximum near 37.8 degrees.
- The 2R+G rule (24-25in / 600-640mm) is the comfort check that pitch alone misses.
- Total run = going x number of treads; a shallower pitch always needs more floor.
- Every riser in a flight must match within 3/8in (or 5mm in the UK).
Pitch is one number from two measurements
The pitch of a staircase is the angle between the pitch line and the floor, and it comes from exactly two figures: the riser height and the going. Divide the riser by the going and take the arctangent. A 190mm riser on a 250mm going is 37.2 degrees; a 7 1/2in riser on an 11in going is 34.3 degrees. Everything else — headroom, total run, how the flight feels underfoot — follows from those same two numbers.
| Riser | Going | Pitch | 2R+G | Feel |
|---|---|---|---|---|
| 6.5in / 165mm | 11in / 280mm | 30.6° | 24.0in | Generous, gentle |
| 7.0in / 178mm | 11in / 280mm | 32.5° | 25.0in | Comfortable |
| 7.5in / 190mm | 10.5in / 267mm | 35.5° | 25.5in | Standard domestic |
| 7.75in / 197mm | 10in / 254mm | 37.8° | 25.5in | IRC maximum |
| 8.5in / 216mm | 9in / 229mm | 43.4° | 26.0in | Over UK limit |
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 calculatorWhere the limits come from
Two codes govern most of the English-speaking world and they arrive at similar places by different routes. The UK states the pitch directly: 42 degrees maximum on a private stair, with a 220mm minimum going and a 220mm maximum rise. The US never mentions an angle — it caps the riser at 7 3/4in and sets a 10in minimum tread, and the geometry does the rest. Design to whichever set applies, then sanity-check with 2R+G.
- UK private stair: rise 150-220mm, going 220mm minimum, pitch 42 degrees maximum.
- US IRC: riser 7 3/4in maximum, tread 10in minimum, nosing 3/4in-1 1/4in on closed risers.
- Headroom: 2000mm in the UK, 6ft 8in in the US, measured vertically off the pitch line.
- Consistency: risers within 3/8in (US) or 5mm (UK) across the whole flight.
When the pitch will not fit the space
The commonest reason people look up pitch is that the flight does not fit. Resist the temptation to steepen it. A stair that clears building control on paper but pitches at 41 degrees is one people avoid carrying anything down, and it is the single most reliable source of falls in a house. The three legitimate fixes are a landing that splits the run, a quarter or half turn that folds it back on itself, and winders that turn while still climbing.
Check headroom at the same time
Steepening a stair to save floor space usually creates a headroom problem at the trimmer instead. Read the headroom figure alongside the pitch before you commit to a riser height.
Pitch and what goes on top of the treads
Pitch changes how a covering behaves. On a steep flight the runner wraps a tighter nose and takes more abrasion at the leading edge, and on a shallow one you see more of the tread and less of the riser as you climb, which changes how a pattern reads. Once the riser and going are settled here, the stair runner calculator on the home page turns them into an exact runner order, and the stair runner length calculator handles landings and pattern repeat.
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.
Still deciding on material, width or pattern? Our hub on stair runners compares weaves, widths, backings and fitting styles side by side, then hands the numbers straight to the calculator.
Frequently asked questions
What is a comfortable stair pitch?
Between 30 and 37 degrees for everyday domestic use. Around 32-35 degrees is the sweet spot most people describe as effortless: the tread is deep enough to take a whole foot and the rise is low enough that the climb does not feel like work. Below 30 degrees a flight starts to feel stretched and eats an unreasonable amount of floor; above 38 degrees people begin descending sideways.
What is the maximum stair pitch allowed?
UK Approved Document K sets 42 degrees as the maximum for a private stair in a dwelling, and no maximum pitch is allowed at all for common or public stairs beyond what the rise and going limits produce. The US IRC does not state a pitch, but capping the riser at 7 3/4in and the tread at a 10in minimum caps the angle at roughly 37.8 degrees in practice.
How do I measure the pitch of an existing staircase?
Lay a straight edge on the nosings so it touches at least three of them — that is the pitch line — and read the angle off a digital level or an angle finder resting on it. Do not measure off a single tread or the stringer face; nosings and stringer profiles vary, and both give an angle a degree or two out from what the stair actually walks like.
What is the 2R+G rule and why does it matter more than pitch?
Twice the riser plus the going should land between 24in and 25in (600-640mm). It matters more than pitch because two flights can share an angle while walking completely differently: a 6in riser on an 8in going and a 7 1/2in riser on a 10in going are both about 36.9 degrees, but the first has a tread too shallow for an adult foot. Check pitch and 2R+G together.
How much floor space does a given pitch need?
Total run equals the going multiplied by the number of treads, so pitch and floor space trade directly against each other. A 2700mm floor-to-floor at 42 degrees needs about 3.0m of run; the same rise at 33 degrees needs about 4.1m. If the run will not fit, the answer is a landing, a quarter turn or winders — not a steeper riser.
Is a steeper pitch allowed for a loft or space-saver stair?
Alternating-tread and space-saver stairs are permitted in the UK for access to a single room in a loft conversion, under tight conditions on headroom, handrails and the room served. They are not a general licence to build a steep flight, and they are not accepted where the stair is the only access to more than one habitable room. Check with building control before you order one.
Is the stair pitch calculator free?
Yes. Pitch, rise, going, total run, headroom and the code checks are free without an account. A free Riser account only adds saving the flight to a project so the same numbers become a quote or a cutting schedule later.
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.