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Geometry & Practical Projects

Staircase Dimension Estimator

Estimate the number of steps, riser height, total run, stringer length and pitch for a straight staircase.

Your inputs

Building codes set limits — e.g. 196 mm (7¾ in) in the US IRC, 220 mm for UK private stairs. Check yours.

Results

Number of risers (steps)

15

Actual riser height
180 mm
Number of treads
14
Total run (horizontal length)
3,500 mm
Approximate stringer length
4,420 mm
Pitch angle
35.75 °
2 × riser + going
610 mm (within the common 600–650 mm comfort range)

≈Estimate based on the stated model and assumptions

Notes for this result

  • Stair geometry is regulated (headroom, nosing, handrails, maximum pitch). Have the design checked against your local building code.

What this calculator does

Equal risers and comfortable proportions make stairs safe. Start from the floor-to-floor rise and your code’s maximum riser.

Formula and method

Risers = ceiling(total rise ÷ max riser); riser = rise ÷ risers; treads = risers − 1; run = treads × going; stringer ≈ √(rise² + run²)

Worked example

Calculated by this tool with its default inputs:

Inputs

  • Total rise (floor to floor): 2700 mm
  • Maximum riser height allowed: 180 mm
  • Tread depth (going): 250 mm

Results

  • Number of risers (steps): 15
  • Actual riser height: 180 mm
  • Number of treads: 14
  • Total run (horizontal length): 3,500 mm
  • Approximate stringer length: 4,420 mm
  • Pitch angle: 35.75 °

How to read the results

The 2 × riser + going “comfort rule” is often kept between about 600 and 650 mm.

Assumptions and limitations

  • Building codes regulate risers, treads, headroom and handrails — have designs checked.

Quantities and costs are planning estimates. Add sensible allowances, and check with suppliers, carriers or professionals before buying, shipping or building.

Questions

Why is there one fewer tread than risers?

The top step is the upper floor itself.

Methodology and verification

Result type
Estimate based on the stated model and assumptions
Formula version
1.0
Automated verification
3 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
Editorial review
Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.

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