Metric stairs
Stair Calculator in Metric: Planning Rise and Run in Millimetres
How to plan stairs in metric units: typical riser and going ranges in millimetres, converting from a total rise, and laying out stringers in mm.
Research Lens
What makes stair calculator in metric: planning rise and run in millimetres useful enough to become a repeatable app workflow?
The strongest app workflows reduce setup, keep private records local, make the next decision visible, and export or share only when the user is ready. The article focuses on the capture-review-output loop behind the app use case.
Decision Metrics
Visual model
Metric stair geometry at a glance
Metric stairs balance riser and going in millimetres the same way imperial stairs balance them in inches, within national code limits.
Metric Stairs Use Rise And Going In Millimetres
Outside North America, stairs are usually designed in millimetres, with the riser height and the going (the horizontal tread depth) specified in mm. The principles are identical to imperial: divide the total rise into equal risers and choose a comfortable going. Only the units and the typical comfort ranges differ.
Typical Riser And Going Ranges
Comfortable metric stairs commonly fall around a riser of roughly 150 to 190 mm and a going of roughly 220 to 260 mm, with exact limits set by your national code, such as the UK's Document K. As with imperial stairs, a taller riser pairs with a shallower going and vice versa, balanced for comfort.
Start From The Total Rise In Millimetres
Measure the total rise from finished floor to finished floor in millimetres. Divide by a target riser height to get a riser count, then divide the total rise by that whole number of risers to get the exact equal riser height. The going is then chosen within the comfortable range and the available run.
The Pitch Still Matters
The pitch, or angle of the stair, follows from the riser and going just as it does in imperial. Steeper stairs save space but are harder to climb. Many codes cap the maximum pitch for private and public stairs. Calculating the pitch from your mm riser and going confirms the stair sits within the allowed angle.
Mixing Units On A Job
Some projects mix imperial lumber with metric design, or vice versa. A stair calculator that switches between inches and millimetres avoids conversion errors, which are a common source of uneven steps. Keep one unit system for the whole stair where you can, and let the tool convert only when a material forces it.
Lay Out The Stringer In Metric
Once the mm riser and going are set, the stringer layout is the same sawtooth pattern, marked in millimetres. A calculator gives the board length, throat depth, and cut marks in metric, and the Stringer app supports both units, so you can design in mm and still get a clean, code-checked cut sheet.
Compare
Imperial vs metric stair planning
| Aspect | Imperial | Metric | Same idea |
|---|---|---|---|
| Riser | ~7 in | ~150-190 mm | Equal risers |
| Going/run | ~10-11 in | ~220-260 mm | Comfortable depth |
| Reference | IRC | Doc K / NCC | Code limits |
| Layout | Inches | Millimetres | Sawtooth stringer |
Field Checklist
- Measure total rise floor to floor in millimetres.
- Target a riser around 150-190 mm per local code.
- Choose a going around 220-260 mm for comfort.
- Confirm the pitch stays within code limits.
- Keep one unit system across the whole stair.
FAQ
Common questions
What is a comfortable riser height in mm?
Commonly around 150 to 190 mm, with the exact range set by your national code. Equal risers across the whole stair matter more than the precise figure.
What is the going on a stair?
The going is the horizontal depth of the tread, the metric equivalent of the run or tread depth, typically around 220 to 260 mm for comfort.
How do I calculate metric stairs from the total rise?
Measure the total rise in mm, divide by a target riser to get a whole riser count, then divide the rise by that count for the exact equal riser height.
Which code applies to metric stairs?
It depends on your country, such as Document K in the UK or the NCC in Australia. Each sets riser, going, pitch, and headroom limits.
Can I mix imperial and metric on one stair?
It is best to keep one unit system to avoid conversion errors. A calculator that switches units helps when a material forces a mix.
Does a stair calculator work in millimetres?
Yes. The Stringer app and calculator support both inches and millimetres, giving cut marks, board length, and throat in your chosen unit.
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