# 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:

1. Determine the population size at the beginning of the period you’re interested in. This is the starting population.
2. Determine the birth rate of the population. This is the number of births per unit of time, usually expressed as a percentage.
3. Determine the death rate of the population. This is the number of deaths per unit of time, usually expressed as a percentage.
4. 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.
5. Determine the length of time you’re interested in. This is the time period over which you want to estimate the population size.
6. 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:

1. Determine the starting population: 100,000.
2. Determine the birth rate: 2% or 0.02.
3. Determine the death rate: 1% or 0.01.
4. Determine the migration rate: 0.5% or 0.005.
5. Determine the length of time: 5 years.
6. 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.