Case Fatality Rate (CFR) – % of diagnosed who die
Crude/Specific Mortality Rate – Deaths per Population
Total deaths attributed to the disease/cause.
Number of confirmed cases of the disease.
The total population at risk (e.g., city or country population).
1,000 People
10,000 People
100,000 People (Standard)
1,000,000 People
Please enter valid positive numbers. The denominator cannot be zero.
Calculated Rate:
0.00%
function toggleMrFields() {
var type = document.getElementById('mr_calc_type').value;
var groupCases = document.getElementById('group_cases');
var groupPop = document.getElementById('group_population');
var groupMult = document.getElementById('group_multiplier');
var resultBox = document.getElementById('mr_result');
var errorBox = document.getElementById('mr_error');
// Reset display
resultBox.style.display = 'none';
errorBox.style.display = 'none';
document.getElementById('mr_deaths').value = ";
document.getElementById('mr_cases').value = ";
document.getElementById('mr_population').value = ";
if (type === 'cfr') {
groupCases.style.display = 'block';
groupPop.style.display = 'none';
groupMult.style.display = 'none';
} else {
groupCases.style.display = 'none';
groupPop.style.display = 'block';
groupMult.style.display = 'block';
}
}
function calculateMortalityRate() {
var type = document.getElementById('mr_calc_type').value;
var deaths = parseFloat(document.getElementById('mr_deaths').value);
var resultBox = document.getElementById('mr_result');
var errorBox = document.getElementById('mr_error');
var displayValue = document.getElementById('mr_final_value');
var explanation = document.getElementById('mr_explanation');
// Basic validation
if (isNaN(deaths) || deaths < 0) {
errorBox.innerHTML = "Please enter a valid number of deaths.";
errorBox.style.display = 'block';
resultBox.style.display = 'none';
return;
}
if (type === 'cfr') {
// Case Fatality Rate Calculation
var cases = parseFloat(document.getElementById('mr_cases').value);
if (isNaN(cases) || cases 0).";
errorBox.style.display = 'block';
resultBox.style.display = 'none';
return;
}
if (deaths > cases) {
errorBox.innerHTML = "Logic Error: Deaths cannot exceed total cases.";
errorBox.style.display = 'block';
resultBox.style.display = 'none';
return;
}
var cfr = (deaths / cases) * 100;
displayValue.innerHTML = cfr.toFixed(2) + '%';
explanation.innerHTML = "This means for every 100 confirmed cases, approximately " + cfr.toFixed(1) + " resulted in death.";
} else {
// Crude/Specific Mortality Rate Calculation
var population = parseFloat(document.getElementById('mr_population').value);
var multiplier = parseFloat(document.getElementById('mr_multiplier').value);
if (isNaN(population) || population 0).";
errorBox.style.display = 'block';
resultBox.style.display = 'none';
return;
}
if (deaths > population) {
errorBox.innerHTML = "Logic Error: Deaths cannot exceed total population.";
errorBox.style.display = 'block';
resultBox.style.display = 'none';
return;
}
var rate = (deaths / population) * multiplier;
var unitText = "";
if (multiplier === 1000) unitText = "per 1,000 people";
else if (multiplier === 10000) unitText = "per 10,000 people";
else if (multiplier === 100000) unitText = "per 100,000 people";
else if (multiplier === 1000000) unitText = "per million people";
displayValue.innerHTML = rate.toFixed(2) + ' ' + unitText + '';
explanation.innerHTML = "In a population of this size, there are approximately " + rate.toFixed(2) + " deaths attributed to this cause for every " + multiplier.toLocaleString() + " people.";
}
errorBox.style.display = 'none';
resultBox.style.display = 'block';
}
How to Calculate Mortality Rate of a Disease
Calculating the impact of a disease is crucial for epidemiologists, public health officials, and medical researchers. Understanding how to calculate the mortality rate helps in assessing the severity of an outbreak, the effectiveness of treatments, and the overall burden on the healthcare system. However, "mortality rate" can refer to different metrics depending on the context.
1. Case Fatality Rate (CFR)
The Case Fatality Rate represents the severity of a disease. It answers the question: "If someone catches this disease, how likely are they to die?" It is commonly expressed as a percentage.
The Formula
CFR (%) = (Number of Deaths from Disease / Number of Confirmed Cases) × 100
Example: In a local outbreak of Influenza, there are 5,000 confirmed cases. Unfortunately, 50 of those patients pass away.
Deaths: 50
Cases: 5,000
Calculation: (50 / 5,000) = 0.01
Percentage: 0.01 × 100 = 1.0% CFR
2. Crude or Cause-Specific Mortality Rate
Unlike CFR, the Mortality Rate measures the burden of death on the entire population, regardless of whether they are sick or healthy. This statistic helps governments plan resources and understand risk at a societal level. Because the result is often a very small decimal, it is usually multiplied by 1,000, 10,000, or most commonly, 100,000.
The Formula
Mortality Rate = (Number of Deaths / Total Population) × Multiplier
Example: A city has a total population of 2,000,000 people. Last year, 400 people died from Heart Disease.
Deaths: 400
Population: 2,000,000
Raw Calculation: 400 / 2,000,000 = 0.0002
Standard Reporting (Per 100k): 0.0002 × 100,000 = 20 deaths per 100,000 people
Key Differences
Metric
Denominator
Purpose
Case Fatality Rate
Diagnosed Cases
Measures biological virulence and treatment efficacy.
Mortality Rate
Total Population
Measures impact on society and public health trends.
Factors Affecting Accuracy
When using the calculator above, keep in mind that data accuracy is vital. Under-reporting of cases (common in asymptomatic diseases) can artificially inflate the Case Fatality Rate because the denominator (total cases) is smaller than reality. Conversely, lag time between diagnosis and outcome can skew rates during an active outbreak.