Staircase Calculator
This staircase calculator helps you plan a comfortable, safe flight of stairs in seconds. Enter the total height you need to climb — the vertical distance from one finished floor to the next — and your preferred riser height, and it instantly returns the number of steps, the actual riser height once the total is divided evenly, and the recommended tread depth. It is ideal for builders, carpenters, DIY renovators and architects roughing out a design for an interior staircase, a deck, a porch or a set of garden steps. Because every riser in a flight must be identical for safety, the tool distributes the total rise across whole steps and shows the real riser you will build, so you can check it against your local building regulations before cutting a single stringer.
Number of steps
Actual riser height (cm)
Recommended tread depth (cm)
Uses the Blondel rule: 2·riser + tread = 63 cm. Always check your local building codes — a comfortable riser is typically 17–19 cm and the tread ideally 25 cm or more.
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How it works
The calculation starts from the total rise, the full vertical height between the two floor levels. First the calculator divides that total rise by your preferred riser height and rounds to the nearest whole number to get the number of steps: steps = round(total rise ÷ preferred riser). It then divides the total rise back by that whole number of steps so every riser is exactly equal: actual riser = total rise ÷ steps. Finally it derives the tread depth from the Blondel rule, a stair-comfort formula stating that two risers plus one tread should equal about 63 cm (one comfortable stride): tread = 63 − 2 × riser. A taller riser therefore yields a shallower tread and vice versa, which is why 17–19 cm risers paired with treads of 25 cm or more feel natural to walk.
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Preguntas frecuentes
- What is the difference between riser and tread?
- The riser is the vertical part of a step — its height, how far you lift your foot from one step to the next. The tread is the horizontal part you actually stand on — its depth from the front edge to the back. A comfortable stair pairs a moderate riser (17–19 cm) with a generous tread (25 cm or more).
- What is the Blondel rule?
- The Blondel rule is a classic stair-comfort formula from 17th-century architect François Blondel: two risers plus one tread should equal roughly 63 cm, the length of an average comfortable stride. It links riser and tread so that steps feel natural to climb — this calculator uses it to suggest a tread depth from your riser height.
- Why does the actual riser differ from the one I entered?
- Every riser in a flight must be identical for safety, and the total height rarely divides evenly by your preferred riser. The calculator rounds to a whole number of steps, then divides the total rise back over those steps, giving a slightly different actual riser that stays perfectly even from bottom to top.
- What is a comfortable and safe step height?
- For interior stairs a riser of about 17–19 cm with a tread of 25 cm or more is widely considered comfortable and safe. Very tall risers make the climb tiring and increase trip risk, while very short ones waste floor space. Always confirm against your local building code, which sets legal maximum and minimum values.
- Can I use this for outdoor steps and decks?
- Yes. The same method applies to garden steps, porches, decks and terraces. Outdoor steps often use slightly lower risers and deeper treads for easier, safer walking, especially in wet conditions, so lower your preferred riser value accordingly and check any local rules for exterior stairs.