Case 1
- Total rise (floor to floor)
- 280cm
- Target riser height
- 18cm
16steps
Open with these valuesStair Calculator
16steps
Result: 16 stepsDivide the floor-to-floor rise by the riser height you want and round to the nearest whole step. A 280 cm rise at an 18 cm target gives 16 steps, so every riser comes out at exactly 17.5 cm. The rounding is what makes them equal, and equal risers are what stop people tripping.
Worked examples
Case 2
- Total rise (floor to floor)
- 300cm
- Target riser height
- 20cm
15steps
Open with these valuesCase 3
- Total rise (floor to floor)
- 250cm
- Target riser height
- 17cm
15steps
Open with these valuesHow it's calculated
steps = round(rise ÷ target riser), at least 1
- StepMeasure the total rise from finished floor to finished floor, in centimetres.
- StepEnter the riser height you are aiming for — 17 to 19 cm is comfortable at home.
- StepRound to the nearest whole step; the rise then divides evenly across them.
- ResultCheck against your building code: this calculator applies no rule of its own.
What this number means
This calculator applies no building rule
It divides the rise by your target height and does nothing else. What a riser, a tread or a headroom may be is set by the building code where you live, and that code overrides anything here. Treat the count as a starting point, never as an approval.
Rounding can go down as well as up
A 100 cm rise at a 19 cm target gives 5.26, which rounds to 5 steps of exactly 20 cm — taller than the target you typed. Read the actual riser off the table before you settle on a count.
Every riser in one flight must be equal
The count is rounded first so that the rise divides evenly: 280 cm over 16 steps is exactly 17.5 cm each. Codes cap the difference between the tallest and the shortest riser in a flight at a few millimetres, because feet learn the rhythm after a step or two.
17 to 19 cm is a convention, not a limit
It is the comfortable range this calculator starts from, and nothing in the formula enforces it. The source behind this page gives 150 to 220 mm as the permissible range in the United Kingdom, which is wider and holds for one country only.
Commonly misread
16 steps at an 18 cm target means every riser is 18 cm.
The target only picks the count. The actual riser is the rise divided by that count: 280 ÷ 16 = 17.5 cm.
The step count from here is enough for a building application.
It divides the rise and applies no rule of its own. The riser, the tread and the headroom you are allowed come from your local building code.
I measured from bare floor to bare floor.
Measure finished floor to finished floor, with the coverings in place. Screed and flooring on either level change the rise and with it the count.
The result gives me the tread depth as well.
No, only the riser height and the step count. Tread depth, total run and headroom are separate dimensions this calculator never touches.
Reference table
| Total rise, target riser | Actual riser | Steps |
|---|---|---|
| 15, 20 | 15 cm | 1 |
| 100, 19 | 20 cm | 5 |
| 250, 17 | 16.67 cm | 15 |
| 270, 17 | 16.88 cm | 16 |
| 280, 18 | 17.5 cm | 16 |
| 300, 20 | 20 cm | 15 |
Questions
How many steps does my staircase need?
Divide the total rise by your target riser height and round to the nearest whole number. A 280 cm rise with an 18 cm target gives 15.56, which rounds to 16 steps.
What is the actual step height?
The total rise divided evenly across the steps: 280 ÷ 16 = 17.5 cm per riser. Rounding the count first is what lets every riser come out identical.
Does this apply the 2R + G stride rule?
No. It divides the rise and does nothing else. The stride formulas — twice the riser plus the going, about 63 cm in Germany, 625 mm in the US and a range of 550 to 700 mm in the UK — size the tread, which this calculator never touches.
Why must every riser be the same height?
Because your feet learn the rhythm of a flight after a step or two and expect it to hold. Codes therefore cap the difference between the tallest and shortest riser in one flight at a few millimetres.
Does it size the tread depth too?
No, only the riser height and the step count. Tread depth, total run and headroom are separate dimensions, set by the building code where you live.
Sources and last check
Information, not professional advice.