The urban size is an important attribute influencing urban population growth and urbanisation. The concentration of population in big cities has been associated with an increasing level of urbanisation. It is a matter of inquiry how bigger cities are growing compared to intermediate and small urban centres. Growth dynamics of urban centres by size class are closely related to the urbanisation cycle. In the early phase, bigger cities are likely to have a higher growth rate, but in the latter phase small towns are expected to grow as a result of increased congestion and crowding in the large and intermediate towns. This chapter throws light on the urban population growth rate by size class of urban centres and the role of rural to urban migration influencing differential urban growth as a component of urbanisation and urban transition.