The basic equation for calculating population growth multiplies the population size by the per capita growth rate, which is calculated by subtracting the per capita death rate from the per capita birth rate. This simplistic calculation does not factor in the effects of migration or immigration on a population's size.
The population growth rate is a measurement of a population's change in size over a period of time. When more people are added to a population than are removed, the population growth rate is positive.
More mathematically precise calculations can be made to more accurately gauge a population's growth. Advanced equations incorporate real-world scenarios and conditions, such as the impact of limited resources