Population Doubling Time Calculator

Population Doubling Time Calculator: How Fast Does It Double?

A quick way to gauge how fast a population is growing is to ask how long it takes to double. This calculator computes the exact doubling time directly from the natural log, more precise than the popular but approximate "rule of 70" shortcut.

The Formula

Doubling Time = ln(2) / r

Worked Example

A population growing at 5% per year.

Doubling Time = 0.6931 / 0.05 = 13.86 years

How to Use This Calculator

1. Enter the annual growth rate as a percentage.
2. Click Calculate to get the exact doubling time in years.

Related Calculations

Use with the Population Growth Rate Calculator to project population size at any point along the way to doubling.