# Prevalence Rate Formula Calculator

Determines the proportion of a particular population that is affected by a medical condition.

In epidemiology, prevalence (also known as Prevalence Rate) defines the proportion of a particular population that is affected by a disease, risk factor or other studied outcome. This can either be measured at a particular time or over a specified period of time.

`Prevalence Rate (%) = New and pre-existing cases of disease during the same time period / Population size during the same time period x 100`

• Point prevalence – P (%) measured at a particular point in time, on a particular date.
• Period prevalence – P (%) measured over an interval of time.

New and pre-existing cases of disease
Population size
*Both of the above figures should be referring to the same time period.
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Steps on how to print your input & results:

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.

In epidemiology, prevalence (also known as Prevalence Rate) defines the proportion of a particular population that is affected by a disease, risk factor or other studied outcome. This can either be measured at a particular time or over a specified period of time.

`Prevalence Rate (%) = New and pre-existing cases of disease during the same time period / Population size during the same time period x 100`

Often confused with incidence, it is important to distinguish that prevalence includes all cases, new and pre-existing, in a population whilst incidence only measures new cases that develop the condition. In relation to the time period, prevalence may be classified as:

• Point prevalence – P (%) measured at a particular point in time, on a particular date.
• Period prevalence – P (%) measured over an interval of time.

A high prevalence of a disease within a population might result from either high incidence or a prolonged rate of survival without a cure or from both these factors.

A low prevalence might result from either low incidence of the condition, rapid mortality or rapid recovery or a combination of these.

The prevalence indicator is preferred to incidence when measuring chronic diseases which are characterised by a long duration and difficulty in pointing out the exact date of onset.

Prevalence is usually reported as a percentage, but may also be found as no out of 100 or as number of cases per 10,000 or 100,000 people.

## References

Centers for Disease Control and Prevention: Principles of Epidemiology in Public Health Practice, Third Edition – An Introduction to Applied Epidemiology and Biostatistics.

Spronk I, Korevaar JC, Poos R, Davids R, Hilderink H, Schellevis FG, Verheij RA, Nielen MMJ. Calculating incidence rates and prevalence proportions: not as simple as it seems. BMC Public Health. 2019; 19(1):512.

Specialty: Epidemiology

Article By: Denise Nedea

Published On: October 26, 2020 · 12:00 AM

Last Checked: October 26, 2020

Next Review: October 26, 2025