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Population Projection (Growth Rate) Calculator

Work out population projection (growth rate) instantly with clear inputs, formula shown and shareable results.

About Population Projection (Growth Rate) Calculator

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.

Formulas

Geometric projection

Pn = P0 x (1 + r)^n

Doubling time

Years = ln 2 / ln(1 + r)

Worked example

With the default values below, Population Projection (Growth Rate) Calculator returns Projected population of 77,266. Change any input above and every figure here is recalculated in your browser.

Inputs used

Current populationminimum 1
50,000
Annual growth rateaccepts -10–20 %
2.2 %
Projection periodminimum 1 years
20 years

Results

Projected population
77,266
Absolute increase
27,266
Doubling time
31.9 years
Projection on arithmetic growth
72,000

Step by step

  1. 1Values used
  2. 2Geometric projection
  3. 3Doubling time
  4. 4Projected population= 77,266
  5. 5Absolute increase= 27,266
  6. 6Doubling time= 31.9 years
  7. 7Projection on arithmetic growth= 72,000

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or fees or charges into account.
  • Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Population Projection (Growth Rate) figure worked out?

Pn = P0 x (1 + r)^n. Geometric projection compounds the growth rate, which suits populations growing by natural increase and migration.

Which method should a master plan use?

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.

What values do I need to enter?

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.

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