What is the case fatality rate (CFR)?

The CFR is the proportion of people with a confirmed diagnosis of a disease who die from it. It is expressed as a percentage: (Deaths / Cases) x 100. It differs from the infection fatality rate (IFR), which includes undetected infections.

Why does CFR overestimate true mortality?

CFR is calculated using only confirmed cases. In most outbreaks, many mild or asymptomatic infections go undetected, so the true number of infections is higher, making the actual fatality risk lower than the CFR suggests.

What is the 95% confidence interval shown?

The Wilson confidence interval reflects uncertainty due to sample size. A smaller case count produces a wider interval. As cases increase, the interval narrows and the CFR estimate becomes more precise.

How does CFR differ from mortality rate?

CFR is calculated per confirmed case, while the mortality rate (deaths per 100,000 population) is calculated per total population. CFR tells you how deadly the disease is for those who get it; mortality rate tells you how deadly it is for the whole population.

Can CFR be above 100%?

No. If deaths exceed cases, the data is inconsistent (deaths may have been counted from a broader group, or case reporting lags behind death reporting). The calculator will flag this as invalid input.

Case Fatality Rate Calculator

Name: Case Fatality Rate Calculator
Availability: InStock
Author: Nham Vu

Enter the number of confirmed cases and deaths to instantly calculate the case fatality rate (CFR) with confidence intervals.

Outbreak Data

Confirmed Cases

Total number of laboratory-confirmed or clinically diagnosed cases.

Deaths

Number of deaths among the confirmed cases.

Confidence Level

Case Fatality Rate

Enter case and death counts to calculate CFR.

CFR Reference — Known Diseases

Seasonal Influenza ~0.1%

COVID-19 (global avg.) ~1–2%

SARS (2003) ~9.6%

MERS ~34%

Ebola (historical) 25–90%

Summary

Enter the number of confirmed cases and deaths to instantly calculate the case fatality rate (CFR) with confidence intervals.

How it works

Enter the total number of confirmed cases in your dataset.
Enter the number of deaths among those confirmed cases.
The calculator instantly computes CFR = (Deaths / Cases) x 100.
A 95% Wilson confidence interval is shown to reflect statistical uncertainty.
Use the severity rating to contextualize the CFR against known disease benchmarks.

Use cases

Epidemiologists tracking mortality during an active outbreak.
Public health officials comparing disease severity across regions.
Medical researchers analyzing historical outbreak data.
Journalists and communicators reporting outbreak statistics accurately.
Students and educators studying infectious disease epidemiology.
Healthcare planners estimating resource needs during an epidemic.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu