Population growth refers to the increase in the number of people in a given area, which can be a neighborhood, country, or even the entire world. The population growth rate is the average change in a population over time, and it can be positive or negative. A positive growth rate indicates a population increase, while a negative growth rate indicates a population decrease. Population growth rates can be calculated by subtracting population loss, or the combined rates of mortality and emigration, from population gain, or the combined rates of fertility and immigration.

Factors affecting population growth include fertility, mortality, and migration. Fertility refers to the number of offspring produced on average by an individual species member under certain environmental conditions over a period of time. Life expectancy, which is affected by factors such as healthcare and nutrition, can also impact population growth. Migration, or immigration to or emigration from a particular location, can also affect population growth.

Population growth dynamics can be graphically depicted in an S-shaped curve, known as a logistic curve. The logistic curve represents an initial lag in growth, a burst of exponential growth, and finally a decline in population growth. When population density is high, mortality tends to increase because of competition for resources, predation, or increased disease transmission, resulting in the plateau in growth at the end of the curve.

The worlds human population experienced exponential growth from the 18th century, but growth rates have been declining since the second half of the 20th century. Although population growth rates vary, the actual global human population growth amounts to around 83 million annually, or 1.1% per year. The world population growth rate peaked in 1963 at 2.2% per year and subsequently declined. In 2017, the estimated annual growth rate was 1.1% .