A staircase looks like one of the simplest things in a house — a row of steps from one floor to the next — until you start measuring. Get the rise height a few millimetres off and the staircase fails inspection or feels uncomfortable underfoot. Get the stringer cut wrong and you waste a 4-metre length of structural timber. The Chippy Tools stair calculator does the arithmetic for you in metric or imperial, accounts for the maximum and minimum rise rules in your region, and returns the stringer length, going length, base length, and tread count for any straight-flight staircase from a 600mm garden step up to a 3-metre full storey rise.
What the stair calculator does
The Chippy Tools stair calculator takes one mandatory measurement — the total rise (the vertical distance from finished floor to finished floor) — and returns the rise count, the actual rise height per step, the going (tread depth), the total base length (run), and the stringer length. Optional inputs let you set a target rise height, a maximum rise, a minimum rise, and a target going to match your local building code or personal preference. The app runs locally on iOS and Android with no internet required, so the calculation works on any job site whether you have signal or not.
The same calculator handles interior stairs, deck stairs, garden steps, basement stairs, and the bottom flight of a switchback staircase. For more complex layouts — landings, switchbacks, winders — calculate each straight flight independently using the relevant total rise for that section.
Stair anatomy: rise, going, and stringer
A straight-flight staircase is essentially a right triangle. The vertical edge is the total rise (floor-to-floor height). The horizontal edge is the total run or base length. The hypotenuse is the stringer — the structural board that the treads and risers attach to. Inside the triangle, the staircase profile is the familiar zig-zag of horizontal treads and vertical risers.
In the diagram: (1) total rise, (2) total run, (3) stringer, (4) single rise, (5) going / tread.
A single rise is the vertical height between two consecutive treads. A single going is the horizontal depth of one tread (sometimes called the “run” of a single step, distinct from the total run). The tread is the physical board you step on — its actual depth is usually slightly larger than the going to allow for a nosing overhang at the front. The riser is the vertical board between two treads (open-riser stairs omit it).
The number of rises is one greater than the number of goings — there’s no going at the very top of the flight because you step directly onto the upper floor. So a staircase with 14 rises has 13 goings.
How to calculate stair rise and run
The stair-calculation workflow is straightforward:
- Measure the total rise — vertical floor-to-floor distance. This is the only input the Chippy Tools calculator strictly requires.
- Pick a target rise height — typically 180mm (7-3/32") for residential work, somewhere between your local minimum and maximum rise.
- Divide total rise ÷ target rise — round to the nearest whole number to get the rise count.
- Back-solve the actual rise — total rise ÷ rise count gives the actual per-step rise height.
- Verify the rise sits inside your local code’s min/max range — if not, add or remove a step and repeat.
For a worked example, take a 2,700mm floor-to-floor rise. Target rise 180mm: 2700 ÷ 180 = 15. Round to 15. Back-solve: 2700 ÷ 15 = 180mm exact — perfect. The staircase needs 15 rises (15 risers) and therefore 14 goings (14 treads). Picking a 250mm going gives a base length of (14 × 250) + 250 = 3750mm — wait, that’s not quite right. The base length is the going count × the going depth, plus the depth of the bottom riser if you’re projecting from the wall: (14 × 250) = 3500mm of horizontal run. The Chippy Tools calculator handles this geometry exactly so you don’t have to debate going-from-edge vs going-to-edge in your head on site.
Calculate Stairs On the Job Site
Download Chippy Tools and use the stair calculator on iOS or Android. Offline, fast, and accurate — no signal required to set out a staircase.
How to calculate stair stringer length
The stringer length is the diagonal distance from the bottom of the lowest tread cut to the top of the upper landing cut. Because a straight staircase forms a right triangle, the stringer length is just the hypotenuse: stringer = √(total rise² + total run²).
For the 2,700mm × 3,500mm example above, the stringer length is √(2700² + 3500²) = √(7,290,000 + 12,250,000) = √19,540,000 ≈ 4,420mm. In imperial: a 9-foot rise and 11.5-foot run gives a √(81 + 132.25) ≈ √213.25 ≈ 14'7" stringer. Round up to the nearest standard timber length (4.8m or 16’) when ordering, since you’ll lose a few centimetres at each end to the cuts.
The Chippy Tools stair calculator returns the stringer length directly so you can quote material before you cut. If you’re using engineered LVL or laminated stringers instead of solid timber, the same length applies; just confirm the standard-length availability with your supplier before sizing the staircase to suit.
Calculating stairs for a deck
Deck stairs use exactly the same math as interior stairs, with one extra consideration: the bottom step typically lands on a concrete pad or paver, not a finished floor. Measure the total rise from the top of the deck surface down to the top of the bottom paver (or finished ground level if you’re stepping straight onto compacted dirt or gravel).
A typical 600mm-high deck wants 3 rises at 200mm each — the bottom step lands on a 600×900 paver at ground level, and you take three 200mm steps up to the deck surface. A taller 1,200mm-high deck wants 6–7 rises, and at that height you should add a handrail per most building codes. The Chippy Tools stair calculator handles deck-stair geometry directly — enter the total rise and the app returns the rise count, going, and stringer length to match.
For deck stairs, two important notes: (1) The bottom of each stringer should rest on a non-rotting bearing surface, typically a concrete paver or galvanised post-shoe; never bury the stringer in dirt. (2) The top of each stringer attaches to the deck rim joist via a hangered connection or notched cleat — confirm the connection method with your local code before cutting.
Stairs with a landing
A landing breaks a straight flight into two shorter flights joined by a horizontal pad. Landings are required in some jurisdictions when the total rise exceeds a threshold (typically 3.6m in the AU NCC, 12 risers under the US IRC). They’re also useful for changing direction at 90° or 180° in tight stairwells.
To calculate stairs with a landing, treat the staircase as two separate runs and calculate each one independently. The total rise of the upper run is the floor-to-landing height; the total rise of the lower run is the landing-to-floor height. The two stringers are sized separately and bear on the landing’s framing. The landing pad itself adds horizontal depth to your total run — typically 900mm to 1200mm of landing depth on top of the combined goings.
Run the Chippy Tools stair calculator twice — once per flight — to get two stringer lengths and two rise/going schedules. Add the landing depth manually to the total run when working out floor-space requirements.
Stair Maths That Just Work
Chippy Tools handles stair calculations, deck stairs, landings, decking layout, and balustrade spacing in one app. Download once, calculate anywhere — no internet required.
Building code requirements for stair rise and tread
Stair codes vary significantly by region — always confirm with your local council or building authority before construction. Common limits include:
Australia (NCC Volume Two) — maximum rise 190mm, minimum rise 115mm, minimum going 240mm, maximum going 355mm. The 2R + G rule (twice the rise plus the going) must be between 550mm and 700mm.
United Kingdom (Approved Document K) — private stairs maximum rise 220mm, minimum going 220mm. The pitch must not exceed 42°. Separate, stricter limits apply to common stairs in flats.
United States (IRC) — maximum rise 7-3/4" (≈ 197mm), minimum tread depth 10" (≈ 254mm). Variation between any two adjacent rises must be no more than 3/8" (≈ 9.5mm).
New Zealand (NZBC D1) — maximum rise 190mm, minimum going 280mm for private stairs.
The Chippy Tools stair calculator lets you override the default min/max rise so the result respects whichever code applies to your project. If you’re unsure which limits apply, default to the strictest of: local code, AS 1657 (industrial), or the manufacturer’s spec for prefabricated stair components.
Imperial and metric units
Chippy Tools accepts millimetres, centimetres, metres, feet, inches, or feet and inches in any combination. Enter your total rise in inches and your target going in millimetres in the same calculation if you like — the app converts internally. This is particularly useful when buying timber from a metric supplier in a country that still measures floor heights in feet and inches (Canada, parts of the Caribbean, etc).
The default rise and going values follow Australian convention (180mm target rise, 250mm target going) but every input accepts a custom value, so you can set US IRC defaults (7" / 11"), UK defaults (190mm / 240mm), or your own preferred set once and reuse them on every job.
Why use a stair calculator on your phone
The Chippy Tools app is built for tradespeople who need calculations on-site without internet. The stair calculator is paired in the same app with the Decking Calculator, Baluster Spacing Calculator, and Roof Pitch Calculator — calculate the deck, the deck stairs, the deck balustrade, and the verandah pitch in one workflow without re-entering measurements.
Web-based stair calculators break in basements with no signal and on remote new-build sites where 4G is patchy. The Chippy Tools calculator runs locally on your phone or tablet — the answer is on screen in under a second. Switch between metric and imperial without restarting, save common stair presets for the rise/going values you use most, and pull up the calculator straight from your home screen widget when a customer asks for a quick price during the quote.
Related calculators
- Decking Calculator — for sizing deck boards, joists, and bearers when the staircase ties into a deck
- Baluster Spacing Calculator — for stair handrail balustrades that pair with the staircase
- Roof Pitch Calculator — for verandah, eave, and roof pitches, which use the same rise-over-run math
- Triangle Calculator — for any general right-triangle problem when you need a quick stringer length without the full stair workflow