Free · Epidemiology calculators 👥

New Cases per Population Scale

Calculate a crude period incidence rate from new cases and a population denominator, using preset or custom population scales.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Health results are educational estimates, not a diagnosis or treatment recommendation. A qualified clinician can interpret measurements in the context of your health.

Formula and method

50 new cases among 10,000 people gives 500 cases per 100,000 for the specified reporting period.

Period rate per selected scale = new cases ÷ population × scale.

Worked example

Enter these known values and leave the other values blank.

Total number of new cases
50
Total population at risk
10000
Incidence rate
500

Assumptions and limitations

  • Specify a reporting period outside the numeric fields and use cases and population for that same period and population definition. This model calculates a crude population-based rate; it does not include person-time, adjust for age, estimate uncertainty or count prevalent cases.
  • Enter measured case and population counts as whole numbers. The denominator must be positive; a zero new-case count gives a zero rate. Algebraic inverses may yield a fractional implied count, which is outside the measured-count domain.

Common questions

Is this a person-time incidence rate?

No. Its denominator is a population count. A person-time rate requires summed time at risk, which this model does not collect.

Can I use a custom scale?

Choose the custom-scale control and enter a positive reporting scale. That scale changes the reported magnitude, not the observed case fraction.

References

Case counts are exact nonnegative integers and measured population counts are exact positive integers; zero new cases is valid. This is a population-based period rate, not a person-time rate.

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