Welcome to our exponential growth calculator, a powerful tool to determine the exponential increase in quantity over time. You can also use it to calculate the exponential decay - the exponential decrease in quantity over time! Read through this article to learn about the exponential growth function and exponential growth formula.

What is exponential growth function?

Exponential growth is the increase in quantity over time such that the change is exponential in nature. The formula for exponential growth is:

x(t)=x0(1+r100)tx(t) = x_0 \cdot \left( 1 + \frac{r}{100}\right)^t


  • x(t)x(t) - The quantity as a function of time (at time tt);
  • x0x_0 - The initial value of the quantity (at time t0t_0); and
  • rr - The growth rate (or rate of change).

Note that we assume the rate of change is a constant. Since the time variable tt is an exponent over the rate of change rr, we can surmise that the change in quantity will be drastic over extended periods, far greater than linear and polynomial growth.

We can use Logarithm to find the time tt if the other parameters are known.

How to calculate exponential growth

A town with a population of 5000 grows steadily at 6%6\%. Let's use the exponential growth equation to find the population after 3, 6, 9,12, and 15 years.

Substituting the initial value of 5000 and the growth rate of 6%, we get:

x(t)=5000(1+6100)tx(t) = 5000 \cdot \left( 1 + \frac{6}{100}\right)^t

Now let's evaluate this population growth formula for the different periods and tabulate it.

Population growth over time.

Time in years












Try calculating the same problem with a 10%10\% growth rate. For greater growth rates, you will notice a steeper increase over time.

The exponential growth rate helps calculate the population growth of bacteria, viruses, plants, and animals. Hence, the population growth formula can use the exponential growth model. We also use exponential growth models to calculate the air pressure at different altitudes and compound interest.

Now that you know how to calculate exponential growth let's focus on exponential decay.

Calculating exponential decay formula

Exponential decay is a decrease in quantity over time. The formula for exponential decay is:

x(t)=x0(1r100)tx(t) = x_0 \cdot \left( 1 - \frac{r}{100}\right)^t

In other words, we can calculate exponential decay using the exponential growth equation, but with a negative rate of change.

x(t)=x0(1+r100)tx(t) = x_0 \cdot \left( 1 + \frac{-r}{100}\right)^t

How to use this exponential growth calculator

This exponential growth calculator is a versatile tool that is easy to use:

  • Enter the initial value x0x_0.
  • Provide the rate of change rr. For calculating exponential growth, the rate must be positive. For calculating exponential decay, the growth must be negative.
  • Enter the elapsed time tt. Note that you can use a negative time to find the value at an earlier time.
  • This exponential growth calculator will automatically calculate the final value x(t)x(t).

This calculator can function backward! Enter any three known values in any order to find the remaining unknown.

Krishna Nelaturu
Exponential growth formula
Initial value x₀
Rate of change r
Elapsed time t
Final value x(t)
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