#fit-calculator-wrapper box-sizing: border-box;
.fit-calc-box {
background: #f9f9f9;
border: 1px solid #e1e1e1;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.fit-calc-title {
text-align: center;
font-size: 24px;
margin-bottom: 25px;
color: #2c3e50;
font-weight: 700;
}
.fit-form-group {
margin-bottom: 20px;
}
.fit-form-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #444;
}
.fit-form-group input {
width: 100%;
padding: 12px;
border: 1px solid #ddd;
border-radius: 4px;
font-size: 16px;
transition: border-color 0.3s;
}
.fit-form-group input:focus {
border-color: #0073aa;
outline: none;
}
.fit-calc-btn {
display: block;
width: 100%;
padding: 15px;
background-color: #0073aa;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background-color 0.3s;
}
.fit-calc-btn:hover {
background-color: #005177;
}
.fit-results {
margin-top: 25px;
padding: 20px;
background: #fff;
border: 1px solid #eee;
border-radius: 4px;
display: none;
}
.fit-result-item {
display: flex;
justify-content: space-between;
align-items: center;
padding: 10px 0;
border-bottom: 1px solid #eee;
}
.fit-result-item:last-child {
border-bottom: none;
}
.fit-result-label {
font-weight: 600;
color: #555;
}
.fit-result-value {
font-weight: 700;
color: #0073aa;
font-size: 18px;
}
.fit-error {
color: #dc3232;
text-align: center;
margin-top: 10px;
display: none;
}
.fit-article h2 {
font-size: 28px;
margin-top: 40px;
margin-bottom: 20px;
color: #23282d;
}
.fit-article h3 {
font-size: 22px;
margin-top: 30px;
margin-bottom: 15px;
color: #23282d;
}
.fit-article p {
margin-bottom: 20px;
font-size: 16px;
}
.fit-article ul {
margin-bottom: 20px;
padding-left: 20px;
}
.fit-article li {
margin-bottom: 10px;
}
.fit-formula {
background: #f0f0f1;
padding: 15px;
border-radius: 4px;
font-family: monospace;
margin-bottom: 20px;
overflow-x: auto;
}
function calculateFIT() {
var failuresInput = document.getElementById('fitNumFailures');
var unitsInput = document.getElementById('fitSampleSize');
var durationInput = document.getElementById('fitTestDuration');
var errorDiv = document.getElementById('fitError');
var resultsDiv = document.getElementById('fitResults');
var failures = parseFloat(failuresInput.value);
var units = parseFloat(unitsInput.value);
var duration = parseFloat(durationInput.value);
// Validation
if (isNaN(failures) || isNaN(units) || isNaN(duration) || units <= 0 || duration <= 0 || failures < 0) {
errorDiv.style.display = 'block';
resultsDiv.style.display = 'none';
return;
}
errorDiv.style.display = 'none';
resultsDiv.style.display = 'block';
// Calculations
var totalDeviceHours = units * duration;
// FIT = (Failures / Total Device Hours) * 10^9
// 10^9 is 1,000,000,000
var fitValue = (failures / totalDeviceHours) * 1000000000;
// MTBF (Hours) = 1 / Failure Rate (lambda)
// Failure Rate (lambda) = failures / totalDeviceHours
// Or MTBF = 10^9 / FIT
var mtbfHours = 0;
var mtbfYears = 0;
if (failures === 0) {
// Technically infinite, but for display purposes often represented differently
// Here we will calculate based on FIT being 0
fitValue = 0;
// For MTBF with 0 failures, strictly it's undefined (infinity),
// but usually people use a confidence interval or assume 1 failure for a "floor" estimate.
// For this basic calculator, we will display logic for Infinity.
} else {
mtbfHours = 1000000000 / fitValue;
mtbfYears = mtbfHours / (24 * 365);
}
// Formatting
document.getElementById('resTotalHours').innerText = totalDeviceHours.toLocaleString() + ' hrs';
document.getElementById('resFit').innerText = fitValue.toFixed(2);
if (failures === 0) {
document.getElementById('resMtbfHours').innerText = "Infinite (Theoretical)";
document.getElementById('resMtbfYears').innerText = "Infinite (Theoretical)";
} else {
document.getElementById('resMtbfHours').innerText = Math.round(mtbfHours).toLocaleString();
document.getElementById('resMtbfYears').innerText = mtbfYears.toFixed(2);
}
}
Understanding Failure Rate FIT Calculation
In reliability engineering, accurately quantifying the lifespan and reliability of electronic components is crucial for quality assurance and safety. The Failure Rate FIT Calculator is designed to help engineers converts test data into standard reliability metrics: FIT (Failures In Time) and MTBF (Mean Time Between Failures).
What is FIT?
FIT stands for Failures In Time. It is a standard unit used in the semiconductor and electronics industry to define the failure rate of a component. One FIT equals one failure per billion (1,000,000,000) device-hours.
Because modern electronic components are extremely reliable, using percentage failures per hour results in incredibly small numbers that are hard to work with (e.g., 0.0000001%). FIT scales this up to a readable integer. For example, a component with 10 FIT is expected to have 10 failures if you ran one billion devices for one hour (or one device for one billion hours).
The FIT Formula
The calculation is based on the relationship between the number of observed failures and the total operating time of the sample set. The formula used in this calculator is:
FIT = (Number of Failures / Total Device Hours) × 1,000,000,000
Where:
- Number of Failures: The count of units that failed during the test period.
- Total Device Hours: Calculated as (Sample Size) × (Test Duration per Unit).
Relationship Between FIT and MTBF
MTBF (Mean Time Between Failures) is the inverse of the failure rate. While FIT expresses how many failures occur in a fixed time, MTBF expresses the average expected time before a failure occurs.
MTBF (Hours) = 1,000,000,000 / FIT
Low FIT scores correspond to high MTBF values, indicating higher reliability.
Example Calculation
Suppose you are testing a new voltage regulator. You test 1,000 units for a duration of 1,000 hours each. During this test, 2 units fail.
- Total Device Hours: 1,000 units × 1,000 hours = 1,000,000 hours.
- Failure Rate (raw): 2 / 1,000,000 = 0.000002 failures per hour.
- FIT Calculation: 0.000002 × 1,000,000,000 = 2,000 FIT.
- MTBF Calculation: 1,000,000,000 / 2,000 = 500,000 hours (approx. 57 years).
Why is this important?
For mission-critical applications (such as automotive, aerospace, or medical devices), components typically require very low FIT rates (often single digits or less). Consumer electronics may tolerate higher FIT rates. By using this calculator, quality engineers can standardize their reporting and compare the reliability of components from different batches or manufacturers.