How do you calculate population growth rate?

Use the compound annual growth rate: divide the ending population by the starting one, raise the result to the power of one over the number of years, then subtract one. Dividing total change by years overstates it, because growth compounds.

What is a normal population growth rate?

Across UK local authorities the median since 2001 is about 0.64% a year. The fastest, City of London, has managed 3.18%, and ten authorities have a negative rate.

How long does it take a population to double?

Divide the natural log of 2 by the natural log of one plus the rate. At 1% a year that is about 70 years; at 2% about 35.

Is this a population projection?

No. It compounds a single rate forward. Official projections model births, deaths and migration by age group, because a young population and an old one behave differently at the same current rate.

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Population growth calculator

By James Burfield, SEO consultant, Bath · Page updated 18 September 2026

Work out what a population becomes at a given growth rate, or what rate got it from one figure to another. Load any UK local authority to start from real numbers.

Start from a real place (optional)

Project forward Find the growth rate

Starting population

Growth rate (% a year)

Ending population

Years

This is arithmetic, not a forecast. It compounds a single rate forward. Real population projections, like the ONS's, model births, deaths and migration separately for each age group, because a town full of 25-year-olds and a town full of 75-year-olds do not behave the same way at the same current growth rate. Use this to understand a rate, not to predict a town.

How population growth is calculated

Growth compounds, so you cannot simply divide the total change by the number of years. The standard measure is the compound annual growth rate:

rate = (end ÷ start)^1/years − 1

Take City of London, the UK's fastest-growing local authority. It went from 7,359 residents in 2001 to 15,111 in 2024, which is 105.3% in total. Divide that by 23 years and you would get 4.58% a year, which is wrong. The compound rate is 3.18%, because each year's growth builds on the last.

Going the other way, a population growing at rate r after n years is start × (1 + r)ⁿ. Doubling time is ln(2) ÷ ln(1 + r), which is where the familiar rule of thumb comes from: at 1% a year a population doubles in about 70 years, at 2% in about 35.

Why the rate matters more than it looks

Small annual rates produce large changes over a working lifetime. Across the 361 UK local authorities the median rate since 2001 is around 0.64% a year, which sounds negligible and compounds to roughly a sixth over 23 years. City of London at 3.18% more than doubled.

Ten of the 361 have a negative rate. You can put a minus sign in the box above and see what that does over a few decades: it is the same arithmetic, and it is why shrinking places are hard to reverse once the young have gone.

Real rates to try

Every UK authority's actual rate is in the picker above, computed from official ONS mid-year estimates. The extremes: City of London at 3.18%, and Kensington and Chelsea at -0.50%.