# Population calculator

# Population calculator

**A population calculator is a tool used to estimate the size of a population. Here are the steps to use a population calculator:**

- Determine the population size at the beginning of the period you’re interested in. This is the starting population.
- Determine the birth rate of the population. This is the number of births per unit of time, usually expressed as a percentage.
- Determine the death rate of the population. This is the number of deaths per unit of time, usually expressed as a percentage.
- Determine the migration rate of the population. This is the number of people entering or leaving the population per unit of time, usually expressed as a percentage.
- Determine the length of time you’re interested in. This is the time period over which you want to estimate the population size.
- Use the population growth formula to estimate the population size at the end of the time period.

**The population growth formula is:**

**Population at time t = Starting population * (1 + (birth rate – death rate + migration rate)/100)^t**

Here’s an example to illustrate how to use a population calculator:

Suppose you want to estimate the population of a city after 5 years. The starting population is 100,000, the birth rate is 2%, the death rate is 1%, and the migration rate is 0.5%.

**To estimate the population after 5 years, you would follow these steps:**

- Determine the starting population: 100,000.
- Determine the birth rate: 2% or 0.02.
- Determine the death rate: 1% or 0.01.
- Determine the migration rate: 0.5% or 0.005.
- Determine the length of time: 5 years.
- Use the population growth formula:

Population at time t = Starting population * (1 + (birth rate – death rate + migration rate)/100)^t Population at time 5 years = 100,000 * (1 + (0.02 – 0.01 + 0.005)/100)^5 Population at time 5 years ≈ 107,784

Therefore, the estimated population of the city after 5 years is approximately 107,784.