Free tool
Garden stair calculator
Enter how much you need to climb and we tell you how many steps you need, how big they are and how much ground the stair takes. Everything is calculated in your browser: nothing is sent.
How we calculate
- We divide the level difference by the step height you chose and round to the nearest whole number of steps. All steps in a flight have the same height.
- The tread comes from Blondel’s rule: two risers plus one tread add up to about 63 cm, the length of a stride. We never let it drop below 28 cm.
- The horizontal length is the number of treads (one fewer than risers, because the last step lands on the upper level) plus 1 m for each landing.
- As a reference we use the Spanish building code values (CTE DB-SUA 1, stairs and ramps for general use): risers of 13 to 18.5 cm, treads of 28 cm or more, 2R + T between 54 and 70 cm, at least 3 steps and at most 3.20 m per flight, ramps up to 12 %. Stairs for restricted use, such as those inside a house, allow less demanding values; outdoors the general-use sizes are more comfortable.
What the calculator does not do
It does not design walls, foundations or handrails, and it does not replace the project. If the stair runs beside a retaining wall or climbs more than one storey, the professional who signs the works must check it.
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Frequently asked questions
How many steps do I need to climb 1 metre?
With comfortable steps of about 16.5 cm, six steps of 16.7 cm. With treads of about 30 cm, the stair takes around 1.5 m on plan.
What is Blondel’s rule?
A classic relation between tread and riser: two risers plus one tread should equal one stride, about 63 cm. So the lower the riser, the deeper the tread.
How steep can a garden ramp be?
As a reference, the Spanish code limits general-use ramps to 12 %, and on accessible routes to 10 % for runs under 3 m, 8 % for runs under 6 m and 6 % otherwise.