๐Population Growth Calculator
Model exponential or logistic growth from initial population, growth rate, and time.
Runs entirely in your browser. No data is sent to a server.
Free Population Growth Calculator
Modeling population dynamics for a biology class or ecology project? Our free population growth calculator handles both exponential and logistic growth models. Enter your starting population, growth rate, and time period, and get the projected population instantly โ plus a chart showing exactly how the curve develops over time.
Switch to logistic growth to add a carrying capacity and see how growth slows as the population approaches its environmental limit. Doubling time is calculated automatically for exponential growth, and a full table of values at regular time intervals shows the whole trajectory, not just the endpoint.
Whether you're studying ecology, working through a population genetics problem set, or modeling real-world growth data, this calculator gives you accurate results with the underlying formulas shown. Free, instant, no sign-up required. See the About page or the FAQ for more.
About the Population Growth Calculator
Features
Two models
Exponential (continuous or discrete) and logistic.
Doubling time
Computed automatically for exponential growth.
Carrying capacity
Shown as a reference line in logistic mode.
Solve-for-unknown
Back-calculate growth rate from Nโ, N(t), and t.
Frequently Asked Questions
How does the population growth calculator work?
Choose exponential or logistic growth, enter your starting population, growth rate, and time, and it calculates the resulting population with a chart of the full curve.
What's the difference between exponential and logistic growth?
Exponential growth assumes unlimited resources and grows without bound; logistic growth includes a carrying capacity, so growth slows as the population approaches that limit.
What is carrying capacity?
The maximum population size an environment can sustain long-term, denoted K in the logistic growth equation.
How is doubling time calculated?
Using ln(2) divided by the growth rate r, giving the time needed for the population to double under continuous exponential growth.
Can it solve for growth rate instead of final population?
Yes, in exponential mode you can solve for r given the initial population, final population, and time.
Does it support discrete (generation-based) growth as well as continuous?
Yes, both continuous exponential (N0e^rt) and discrete geometric growth (N0(1+r)^t) are supported as separate options.
What happens if the growth rate is negative?
The calculator handles population decline the same way, showing a shrinking curve over time.
What if I set carrying capacity lower than the starting population?
This is flagged, since it isn't a meaningful logistic growth scenario.
Is this tool free?
Completely free, no sign-up or downloads.
Does it work on mobile?
Yes, the chart and table are both fully responsive.