Mortality Rate Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/9/2026
The crude mortality rate is calculated with (number of deaths ÷ total population) × 1000, expressed per mille. For 500 deaths in a population of 100,000, the mortality rate is 5‰.
Explanation
The crude mortality rate is a basic demographic and ecological indicator, relating the number of deaths over a given period (usually a year) to the size of the population concerned, expressed per thousand people or individuals rather than as a percentage — a convention that makes generally small rates easier to compare. It's used both in human demography (comparing mortality between countries or over time) and in population ecology (tracking the dynamics of an animal or plant population, alongside the birth rate and growth rate). This rate is called "crude" because it doesn't account for the population's age structure: an older population will naturally have a higher crude mortality rate than a younger one, even with identical life expectancy at each age, simply because it has more people nearing the end of life. To compare mortality between two populations with different age structures more rigorously, demographers use age-standardized rates, which neutralize this structural effect — a more complex method than this calculator, which gives the simple crude rate. For the full dynamics of a population (net growth, accounting for both births and deaths), see our population growth rate calculator.
Example: 500 deaths in a population of 100,000
Inputs
Deaths over the period: 500. Total population: 100,000.
Calculation
Mortality rate = (500 ÷ 100,000) × 1000 = 5‰.
Result
This population's crude mortality rate is 5 per mille.
Frequently asked questions
Why express this rate "per mille" rather than as a percentage?
Because annual mortality rates are generally on the order of a few deaths per thousand individuals, which would give a percentage with several barely-readable decimal places (0.5% rather than 5‰, for example). The "per mille" convention is a widely standard readability choice in demography, without changing the nature of the calculation.
Why is this rate called "crude"?
Because it doesn't account for the age structure of the population studied: with identical life expectancy at each age, an overall older population will mechanically show a higher crude mortality rate than a younger one, simply because it has a larger proportion of people nearing the end of life. Directly comparing crude rates between two populations of very different ages can therefore be misleading without this caveat.
What total population should the calculation be based on if the population changes during the period?
The standard demographic convention is to use the population estimated at the midpoint of the period considered (often July 1st for a calendar year), a reasonable compromise for a population that continuously grows or shrinks, rather than fixing a value at the start or end of the period.
How does the mortality rate relate to how fast a population changes size overall?
The mortality rate only captures deaths; combined with the birth rate, it feeds into the population's net growth rate, and from there into our doubling time calculator, which turns a growth rate into a concrete number of years for the population to double (or, for a shrinking population, to halve).