Formula used
- Riser count = round(Total rise ÷ Preferred riser).
- Actual riser = Total rise ÷ Riser count (adjusted to fit limits).
- Tread count = Riser count − 1 (typical finished landing).
- Actual tread = Total run ÷ Tread count (or preferred tread if run is blank).
- Stair angle = atan(Total rise ÷ Total run), converted to degrees.
- Stringer length = √(Total rise² + Total run²).
- Comfort check uses your selected rule: 2R+T or R+T.
How to use this calculator
- Measure total height from garden grade to the landing level.
- Choose units, then set preferred riser and tread targets.
- Set minimum and maximum ranges to match your project needs.
- Optionally enter total run if space is fixed.
- Press Calculate to see counts, angle, and the step layout.
- Download CSV or PDF for a clean on-site reference.
Example data table
| Scenario | Total Rise | Preferred Riser | Preferred Tread | Risers | Treads | Angle |
|---|---|---|---|---|---|---|
| Short garden step set | 900 mm | 150 mm | 300 mm | 6 | 5 | ~31° |
| Raised patio access | 1200 mm | 160 mm | 320 mm | 8 | 7 | ~28° |
| Steeper slope section | 1500 mm | 175 mm | 270 mm | 9 | 8 | ~35° |
Why rise and run matter outdoors
Garden stairs face moisture, soil movement, and uneven foot traffic. Consistent riser height reduces trips, while adequate tread depth improves balance on wet shoes. For compact paths, a slightly lower riser with deeper treads often feels safer. Use the slope limit to keep pitch manageable on long approaches.
Choosing practical target dimensions
Start with a preferred riser that matches how you naturally step. Many outdoor builds favor wider treads to allow slow turns and carrying loads. If your available horizontal space is fixed, enter total run to force the calculator to fit treads within the footprint. The limits fields help avoid extremes that cause fatigue.
How the calculator selects step counts
Riser count begins by dividing total rise by the preferred riser and rounding to a whole number. The tool then adjusts the count until the actual riser fits your minimum and maximum range. Treads are typically one fewer than risers. When total run is blank, the preferred tread becomes the basis for the layout.
Interpreting angle, stringer, and comfort checks
The stair angle is computed from rise and run, giving a quick feel for steepness. Stringer length is the diagonal cut line for layout. The comfort rule (2×Riser + Tread, or Riser + Tread) is a comparative indicator, not a code substitute. Use notes to spot limits or slope issues.
Using exports for layout and materials
After calculating, download CSV to capture every step’s cumulative rise and run. This table is useful for setting string lines, placing blocks, and checking levels across multiple sections. Download PDF for a one-page site summary. Always verify finished heights after base compaction and add drainage where water collects.
FAQs
1) What should I enter for total rise?
Measure vertically from the finished lower grade to the finished upper landing. If you will add pavers or caps, include that thickness so the final step heights stay consistent.
2) When should I fill in total run?
Use total run when your garden path length is fixed by walls, beds, or property lines. The calculator will size the tread depth to fit that footprint using the tread count.
3) Why are treads one fewer than risers?
In most stair layouts, the top landing acts as the final walking surface. That means you climb the last riser onto the landing rather than onto another tread.
4) What does “nosing” change in the results?
Nosing is recorded per tread for planning and detailing. It helps when you are adding overhanging caps or timber treads, but it does not change run calculations unless you adjust tread depth.
5) My slope warning shows “No.” What should I do?
Reduce steepness by increasing tread depth, adding a landing, or splitting the rise into two flights. You can also lower the preferred riser to increase riser count and soften pitch.
6) Are the comfort rules guaranteed to be safe?
No. Comfort rules are simple heuristics for comparing options. For public access or regulated structures, confirm dimensions, handrail needs, and slip resistance using local requirements and site conditions.