Work out population projection (growth rate) instantly with clear inputs, formula shown and shareable results.
Geometric projection compounds the growth rate, which suits populations growing by natural increase and migration. Arithmetic projection adds a constant increment and suits mature settlements near their capacity. The gap between the two over twenty years is large, which is why the method must be stated alongside the number.
Geometric projection
Pn = P0 x (1 + r)^n
Doubling time
Years = ln 2 / ln(1 + r)
Pn = P0 x (1 + r)^n. Geometric projection compounds the growth rate, which suits populations growing by natural increase and migration.
Usually geometric for the first decade and something flatter beyond, because growth rates decline as a settlement matures. A single compounding rate over thirty years almost always over-projects.
This calculator takes 3 inputs: Current population, Annual growth rate, Projection period. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.