Natural Increase Rate Calculator
Enter demographic data to calculate the Rate of Natural Increase (RNI).
How Is Natural Increase Rate Calculated?
The Natural Increase Rate (NIR), often referred to as the Rate of Natural Increase (RNI), is a key demographic statistic used to measure how quickly a population is growing or shrinking based solely on births and deaths. It excludes the effects of migration (immigration and emigration).
Understanding the NIR helps demographers, governments, and urban planners predict future population sizes, infrastructure needs, and economic shifts.
The NIR Formula
There are two primary ways to calculate the Natural Increase Rate, depending on the data you have available.
Method 1: Using Crude Rates (Most Common)
If you already know the Crude Birth Rate (CBR) and Crude Death Rate (CDR), the formula is straightforward. Since CBR and CDR are expressed "per 1,000 people" and NIR is expressed as a percentage ("per 100 people"), you simply divide the difference by 10.
- CBR: Number of live births per 1,000 people per year.
- CDR: Number of deaths per 1,000 people per year.
Method 2: Using Raw Population Data
If you have the raw numbers for total population, total births, and total deaths, you can calculate the percentage directly:
Step-by-Step Calculation Example
Let's calculate the NIR for a hypothetical country with the following data:
- Total Population: 5,000,000
- Births per year: 120,000
- Deaths per year: 80,000
Step 1: Find the Net Natural Increase
Subtract deaths from births: 120,000 – 80,000 = 40,000 (This is the raw increase).
Step 2: Divide by Total Population
40,000 / 5,000,000 = 0.008
Step 3: Convert to Percentage
0.008 × 100 = 0.8%
Alternatively, using Method 1:
- CBR = (120,000 / 5,000,000) × 1,000 = 24
- CDR = (80,000 / 5,000,000) × 1,000 = 16
- NIR = (24 – 16) / 10 = 8 / 10 = 0.8%
What does the Result Mean?
- Positive NIR: The population is growing naturally.
- Zero NIR: The population is stable (Zero Population Growth).
- Negative NIR: The population is shrinking naturally (more deaths than births).
Doubling Time (Rule of 70)
Once you have the Natural Increase Rate, you can estimate how many years it will take for the population to double in size using the "Rule of 70".
In our example of 0.8%, the doubling time would be approximately 70 / 0.8 = 87.5 years.