The ratio of the going and the rise of a step should be well proportioned to ensure a comfortable access to the stair way.
Following empirical rules may be followed.
Treads/Goings in cm + 2 (rise in cm) = 60
Treads/Goings in cm x (rise in cm) = 400 to 450 approx.
Treads/Goings in cm + (rise in cm) = 40 to 45 approx.
Standard sizes: Tread 30 cm, Rise 14 cm
Other combinations of rise and going can be calculated by subtracting 20 mm from going and adding 10 mm to rise. Thus other combinations of rise and going would be
Rise 15 cm x Tread 28 cm
Rise 16 cm x Tread 26 cm
Rise 17 cm x Tread 24 cm
Generally adopted sizes of steps are
Public buildings: (27 cm x 15 cm) to (30 x 14 cm)
Residential buildings: 25 cm x 16 cm