# What is the rate of natural increase?

Computes the rate of natural increase (RNI): births minus deaths as a percent of the population, from counts or from the crude birth and death rates per 1,000.

- Page: https://www.acalculator.org/statistics/rate-of-natural-increase-calculator
- JSON spec: https://www.acalculator.org/statistics/rate-of-natural-increase-calculator.json
- Version: b9742cff100b

## Default answer

Example with the default inputs (I know the Births and deaths, Live births in the year 12,000, Deaths in the year 8,000, Population 1,000,000): The rate of natural increase is 0.4%, or 4 per 1,000 people in the year.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| from | I know the | Numbers of births, deaths and people, or the crude birth and death rates per 1,000. |
| births | Live births in the year | The number of live births in the population during the year. |
| deaths | Deaths in the year | The number of deaths in the population during the year. |
| pop | Population | The population the rate is based on, usually at the middle of the year. |
| br | Crude birth rate (per 1,000) | Live births per 1,000 people in the year. |
| dr | Crude death rate (per 1,000) | Deaths per 1,000 people in the year. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| rni | Rate of natural increase | (Births − deaths) ÷ population × 100, or (birth rate − death rate) ÷ 10. |
| perThousand | Natural increase per 1,000 people | Birth rate − death rate. |
| increase | Natural increase (births − deaths) | Negative when deaths outnumber births (natural decrease). |
| birthRate | Crude birth rate (per 1,000) | Births ÷ population × 1,000. |
| deathRate | Crude death rate (per 1,000) | Deaths ÷ population × 1,000. |

## Method

RNI (%) = (births − deaths) ÷ population × 100. From rates per 1,000: RNI (%) = (crude birth rate − crude death rate) ÷ 10. Crude birth rate = births ÷ population × 1,000; crude death rate = deaths ÷ population × 1,000.

## Assumptions

- Births and deaths are for one year, and the population is the one the rates are based on, usually at midyear.
- Migration is left out: natural increase counts only births and deaths.
- Arithmetic is exact on the typed decimals; the RNI shows to 3 decimals and the rates to 2, halves up.

## Worked examples

1. from = counts, births = 12,000, deaths = 8,000, pop = 1,000,000 gives rni = 0.4%, perThousand = 4, increase = 4,000, birthRate = 12, deathRate = 8. Source: Population Reference Bureau, Glossary of Demographic Terms (rate of natural increase: the rate at which a population is increasing or decreasing in a year due to a surplus or deficit of births over deaths, as a percentage of the base population; birth rate and death rate: live births and deaths per 1,000 population in a year). https://www.prb.org/resources/glossary/.
2. from = counts, births = 9,500, deaths = 11,200, pop = 850,000 gives rni = −0.2%, perThousand = −2, increase = -1,700, birthRate = 11.18, deathRate = 13.18. Source: Population Reference Bureau, Glossary of Demographic Terms (rate of natural increase: the rate at which a population is increasing or decreasing in a year due to a surplus or deficit of births over deaths, as a percentage of the base population; birth rate and death rate: live births and deaths per 1,000 population in a year). https://www.prb.org/resources/glossary/.
3. from = rates, br = 17, dr = 8 gives rni = 0.9%, perThousand = 9. Source: Population Reference Bureau, Glossary of Demographic Terms (rate of natural increase: the rate at which a population is increasing or decreasing in a year due to a surplus or deficit of births over deaths, as a percentage of the base population; birth rate and death rate: live births and deaths per 1,000 population in a year). https://www.prb.org/resources/glossary/.
4. from = rates, br = 9.2, dr = 10.6 gives rni = −0.14%, perThousand = −1.4. Source: Population Reference Bureau, Glossary of Demographic Terms (rate of natural increase: the rate at which a population is increasing or decreasing in a year due to a surplus or deficit of births over deaths, as a percentage of the base population; birth rate and death rate: live births and deaths per 1,000 population in a year). https://www.prb.org/resources/glossary/.
5. from = counts, births = 25,481, deaths = 21,736, pop = 2,345,678 gives rni = 0.16%, birthRate = 10.86, deathRate = 9.27. Source: Population Reference Bureau, Glossary of Demographic Terms (rate of natural increase: the rate at which a population is increasing or decreasing in a year due to a surplus or deficit of births over deaths, as a percentage of the base population; birth rate and death rate: live births and deaths per 1,000 population in a year). https://www.prb.org/resources/glossary/.

## FAQ

### What is the rate of natural increase?

The rate of natural increase (RNI) is the rate at which a population grows, or shrinks, in a year from the surplus or deficit of births over deaths, as a percent of the population. It leaves out migration.

### How do I calculate the rate of natural increase?

Subtract deaths from births, divide by the population and multiply by 100. A town of 1,000,000 with 12,000 births and 8,000 deaths has an RNI of (12,000 − 8,000) ÷ 1,000,000 × 100 = 0.4%.

### How do I get the RNI from birth and death rates?

Crude birth and death rates are per 1,000 people, so subtract the death rate from the birth rate and divide by 10 to get a percent. A birth rate of 17 and a death rate of 8 give (17 − 8) ÷ 10 = 0.9%.

### Why divide by 10?

A rate per 1,000 people becomes a percent, which is per 100 people, by dividing by 10: 9 per 1,000 is 0.9 per 100, or 0.9%.

### Can the rate of natural increase be negative?

Yes. When deaths outnumber births the population shrinks naturally, a natural decrease. A birth rate of 9.2 and a death rate of 10.6 per 1,000 give an RNI of −0.14%.

### How is the RNI different from the population growth rate?

The growth rate also counts net migration, the people moving in minus the people moving out. A country can have a negative RNI and still grow if more people move in than the natural decrease takes away.

## Sources

- Population Reference Bureau, Glossary of Demographic Terms: rate of natural increase (or decrease), the rate at which a population is increasing (or decreasing) in a given year due to a surplus (or deficit) of births over deaths, expressed as a percentage of the base population; birth rate (crude birth rate), the number of live births per 1,000 population in a given year; death rate (crude death rate), the number of deaths per 1,000 population in a given year; growth rate, which adds net migration. https://www.prb.org/resources/glossary/ (retrieved 2026-10-19)