Well designer stairs should be created in way which fallow certain rules and can guarantee safety and comfort to their user.
Width and rise must be adequate to the length of human step. Which is 60-65 cm.
If we want to change a width of the stair we have to change the rise of the stairs too. Connection with those two should be 2r + w = 60 -65.
Where w is width in cm and r is rise.
The correct rise of the stairs inside the buildings is:
20 cm for stairs which leading to the attic or to the basement
19 cm in single family house and two floor flats
16 cm in the public buildings
17,5 cm in other cases
Number of stairs
In one row there shouldn’t be more than 18 stairs. The reason is the health and safety of their users. One row should have from 9 to 12 stairs. Stairs which are located inside the building shouldn't have less than 3 stair because it’s easy to fall over.
The angle between the pitch line (notional line connecting nosings) and the horizontal. The maximum pitch for domestic stairs is 42°, semi-public stairs, eg factories, offices and common stairs serving more than one dwelling, 38° and public stairs, eg places of public assembly, 33°.