CalculationTime

Stair Calculator

Estimate stair risers, tread going, total run and a 2R+G comfort check from floor height and preferred riser height.

Live math canvas

Your numbers, formula and explanation together

Stair Calculator: 3,225 risers, treads and millimetres. Stair Calculator uses the declared inputs to produce a transparent default result. Total rise: 2,800 millimetres; Preferred riser: 175 millimetres; Tread going: 250 millimetres; Landing allowance: 0 millimetres; primary comparison: 2,800 and 175.

Formula applied

The exact method behind this answer

CalculationTime keeps the method visible so the number can be checked instead of blindly trusted.

Risers = round(total rise ÷ preferred riser). Actual riser = total rise ÷ risers. Treads in a straight flight = max(0, risers − 1). Total run = treads × tread going + landing allowance. Comfort check = 2 × actual riser + tread going.
  1. Apply the formulaRisers = round(total rise ÷ preferred riser). Actual riser = total rise ÷ risers. Treads in a straight flight = max(0, risers − 1). Total run = treads × tread going + landing allowance. Comfort check = 2 × actual riser + tread going.3,225 risers, treads and millimetresStair Calculator uses the declared inputs to produce a transparent default result. Total rise: 2,800 millimetres; Preferred riser: 175 millimetres; Tread going: 250 millimetres; Landing allowance: 0 millimetres; primary comparison: 2,800 and 175.

Your live breakdown

Current inputs in the calculation

These values come from the controls above and update when the calculator changes.

Total rise
2,800 millimetres
Vertical height from finished lower floor to finished upper floor or landing.
Preferred riser
175 millimetres
The target riser height before rounding to a whole number of risers.
Tread going
250 millimetres
Horizontal going per tread/nosing line used for the run estimate.
Landing allowance
0 millimetres
Optional extra horizontal allowance for a landing or clear set-out note.

Resulting answer

3,225 risers, treads and millimetres

Stair Calculator uses the declared inputs to produce a transparent default result. Total rise: 2,800 millimetres; Preferred riser: 175 millimetres; Tread going: 250 millimetres; Landing allowance: 0 millimetres; primary comparison: 2,800 and 175.

Answer
3,225 risers, treads and millimetres
Live support
Stair Calculator uses the declared inputs to produce a transparent default result. Total rise: 2,800 millimetres; Preferred riser: 175 millimetres; Tread going: 250 millimetres; Landing allowance: 0 millimetres; primary comparison: 2,800 and 175.

Assumptions used

What this answer assumes

Use for planning and quote notes only. Confirm code limits before construction.

  • The calculator treats the stair as a simple straight flight for measurement planning.
  • The number of risers is rounded to a whole number because partial risers are not usable in a built stair.
  • A straight flight usually has one fewer tread/going than risers because the upper floor or landing acts as the final step surface.
  • Australian residential example: many new builds use about a 175 mm riser, 250 mm going and a finished staircase width around 900–1000 mm as a practical planning benchmark.
  • Inputs are millimetres. The comfort check shown is the common 2R+G rule of thumb, not a building-code approval.
  • Building codes, maximum riser limits, minimum going, finished width, headroom, handrails, landings, nosings and local permits must be checked separately before construction.

Master’s Tip

How to use the result well

Master’s Tip: measure finished-floor to finished-floor after allowing for floor coverings. A few millimetres of tile, screed or timber can change the exact riser height, and stair risers should be consistent across the flight. Treat 175 mm risers, 250 mm going and 900–1000 mm finished width as an Australian residential planning example, not a compliance certificate.

Printable record

What belongs in the saved calculation

Save the inputs, result, formula, assumptions, page URL and date together so the calculation can be reviewed later.

Total rise
2,800 millimetres
Vertical height from finished lower floor to finished upper floor or landing.
Preferred riser
175 millimetres
The target riser height before rounding to a whole number of risers.
Tread going
250 millimetres
Horizontal going per tread/nosing line used for the run estimate.
Landing allowance
0 millimetres
Optional extra horizontal allowance for a landing or clear set-out note.

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Formula

Risers = round(total rise ÷ preferred riser). Actual riser = total rise ÷ risers. Treads in a straight flight = max(0, risers − 1). Total run = treads × tread going + landing allowance. Comfort check = 2 × actual riser + tread going.

Worked example

Total rise 2,800 mm ÷ preferred riser 175 mm = 16 risers. Actual riser = 2,800 ÷ 16 = 175.0 mm. Treads = 16 − 1 = 15. With 250 mm going, total run = 15 × 250 = 3,750 mm. The comfort check is 2 × 175 + 250 = 600 mm. For an Australian residential planning example, a finished stair width of about 900–1000 mm is a common benchmark to check against the drawings.

Professional note

Master’s Tip: measure finished-floor to finished-floor after allowing for floor coverings. A few millimetres of tile, screed or timber can change the exact riser height, and stair risers should be consistent across the flight. Treat 175 mm risers, 250 mm going and 900–1000 mm finished width as an Australian residential planning example, not a compliance certificate.

Regional and unit assumptions

Australian residential planning benchmark: about 175 mm riser height, 250 mm going and 900–1000 mm finished staircase width. Standard or basis: transparent millimetre set-out arithmetic plus the common 2R+G comfort rule of thumb. This is a planning calculator only; it does not certify compliance with the NCC, local rules, drawings, permits or professional building requirements.

Assumptions and limitations

Methodology & Accuracy

How this calculator is checked

CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.

Formula used

Risers = round(total rise ÷ preferred riser). Actual riser = total rise ÷ risers. Treads in a straight flight = max(0, risers − 1). Total run = treads × tread going + landing allowance. Comfort check = 2 × actual riser + tread going.

Standard or basis

Australian residential planning benchmark: about 175 mm riser height, 250 mm going and 900–1000 mm finished staircase width. Standard or basis: transparent millimetre set-out arithmetic plus the common 2R+G comfort rule of thumb. This is a planning calculator only; it does not certify compliance with the NCC, local rules, drawings, permits or professional building requirements.

Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.

Master's Tip

Master’s Tip: measure finished-floor to finished-floor after allowing for floor coverings. A few millimetres of tile, screed or timber can change the exact riser height, and stair risers should be consistent across the flight. Treat 175 mm risers, 250 mm going and 900–1000 mm finished width as an Australian residential planning example, not a compliance certificate.

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Questions

How do I calculate the number of stair risers?

Divide the total vertical rise by the preferred riser height, then round to a whole number of risers. Divide the total rise by that whole riser count to get the actual riser height.

Why are there usually fewer treads than risers?

In a straight stair, the upper floor or landing acts as the final walking surface, so the flight normally has one fewer tread going than the number of risers.

What does 2R+G mean for stairs?

2R+G means two riser heights plus one going depth. It is a common comfort rule of thumb used to sense-check stair proportions, not a substitute for local code requirements.

Can this stair calculator approve a staircase for building work?

No. It is a measurement and set-out calculator. Check local code rules, permits, headroom, handrails, landing requirements and professional advice before building.

What is a typical Australian residential stair size?

As a practical planning benchmark for new Australian residential builds, use about a 175 mm riser, 250 mm going and a finished staircase width around 900–1000 mm. Confirm the NCC, local rules and project drawings before construction.

What should I print from a stair calculation?

Print the total rise, riser count, actual riser height, tread going, total run, comfort check, date and notes so a builder, homeowner or teacher can review the set-out later.

Calculation note

Stair calculation turns a vertical height into repeated, buildable steps. The arithmetic is simple, but the result matters because small riser differences are easy to feel underfoot and built stairs are controlled by local safety rules.

A stair is a repeated measurement system

The useful first step is turning the finished floor-to-floor height into a whole number of equal risers. Equal risers are important because people expect a regular rhythm when climbing or descending.

Run is a set-out quantity, not just a comfort number

Once the riser count is known, the horizontal run follows from the number of treads and the chosen going. That run estimate helps with floor planning, quotes, landings and whether the stair can physically fit in the space.

Code checks belong outside the quick formula

Building rules can set limits for riser height, tread depth, headroom, handrails, landings and guarding. This page keeps the arithmetic visible while warning that local code approval is a separate requirement.

Sources and further readingOSHA: Stairways and LaddersUK Government: Approved Document K