body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
max-width: 800px;
margin: 0 auto;
padding: 20px;
background-color: #f9f9f9;
}
.calculator-container {
background: #ffffff;
border-radius: 8px;
box-shadow: 0 4px 15px rgba(0,0,0,0.1);
padding: 30px;
margin-bottom: 40px;
border: 1px solid #e0e0e0;
}
.calc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 24px;
font-weight: 700;
}
.input-group {
margin-bottom: 20px;
}
.input-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #555;
}
.input-wrapper {
display: flex;
gap: 10px;
}
.input-wrapper input {
flex: 2;
padding: 12px;
border: 1px solid #ddd;
border-radius: 4px;
font-size: 16px;
}
.input-wrapper select {
flex: 1;
padding: 12px;
border: 1px solid #ddd;
border-radius: 4px;
background-color: #f8f9fa;
font-size: 16px;
}
button.calc-btn {
width: 100%;
padding: 15px;
background-color: #2980b9;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background-color 0.3s;
margin-top: 10px;
}
button.calc-btn:hover {
background-color: #2471a3;
}
.results-container {
margin-top: 25px;
padding: 20px;
background-color: #f1f8ff;
border-radius: 6px;
border-left: 5px solid #2980b9;
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
margin-bottom: 12px;
border-bottom: 1px solid #dae1e7;
padding-bottom: 8px;
}
.result-row:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
.result-label {
color: #555;
font-weight: 500;
}
.result-value {
font-weight: 700;
color: #2c3e50;
}
.final-result {
font-size: 1.2em;
color: #27ae60;
}
.article-section {
background: #fff;
padding: 30px;
border-radius: 8px;
box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}
h2 {
color: #2c3e50;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
margin-top: 30px;
}
h3 {
color: #34495e;
margin-top: 20px;
}
p {
margin-bottom: 15px;
}
.formula-box {
background-color: #f4f6f7;
padding: 15px;
border-radius: 5px;
font-family: monospace;
margin: 15px 0;
border-left: 3px solid #7f8c8d;
}
.error-msg {
color: #c0392b;
font-size: 14px;
margin-top: 5px;
display: none;
}
ul {
margin-bottom: 20px;
padding-left: 20px;
}
li {
margin-bottom: 8px;
}
function calculateProRata() {
// 1. Get Elements
var priceInput = document.getElementById("purchasePrice");
var lifeInput = document.getElementById("warrantyLife");
var lifeUnit = document.getElementById("warrantyUnit");
var usedInput = document.getElementById("timeUsed");
var usedUnit = document.getElementById("timeUsedUnit");
var resultsDiv = document.getElementById("resultsArea");
var errorDiv = document.getElementById("errorMsg");
// 2. Parse Values
var price = parseFloat(priceInput.value);
var lifeValue = parseFloat(lifeInput.value);
var lifeMultiplier = parseInt(lifeUnit.value);
var usedValue = parseFloat(usedInput.value);
var usedMultiplier = parseInt(usedUnit.value);
// 3. Validation
if (isNaN(price) || isNaN(lifeValue) || isNaN(usedValue) || price < 0 || lifeValue <= 0 || usedValue = totalMonths) {
document.getElementById("usagePercentResult").innerHTML = "100%";
document.getElementById("depreciatedAmountResult").innerHTML = "$" + price.toFixed(2);
document.getElementById("refundResult").innerHTML = "$0.00";
resultsDiv.style.display = "block";
return;
}
// Calculate usage ratio
var usageRatio = usedMonths / totalMonths;
var depreciatedAmount = price * usageRatio;
var refundAmount = price – depreciatedAmount;
var usagePercent = usageRatio * 100;
// 6. Display Results
document.getElementById("usagePercentResult").innerHTML = usagePercent.toFixed(2) + "%";
document.getElementById("depreciatedAmountResult").innerHTML = "$" + depreciatedAmount.toFixed(2);
document.getElementById("refundResult").innerHTML = "$" + refundAmount.toFixed(2);
resultsDiv.style.display = "block";
}
Understanding Pro Rata Depreciation
Pro rata depreciation is a method used widely in insurance, warranty claims, and asset valuation to determine the remaining value of an item based on its usage over time. Unlike standard amortization, which might be used for tax purposes, pro rata calculations are typically used to calculate a refund or credit amount when a product fails before its expected lifespan ends.
How the Pro Rata Calculator Works
This calculator determines the residual value of your product by comparing the amount of time you used the product against its total expected lifespan (or warranty period). The result is often referred to as a "Pro Rata Credit" or refund.
Credit = Original Price × ((Total Life – Time Used) / Total Life)
This formula ensures that you only pay for the portion of the product's life that you actually consumed, and you are refunded for the unused portion.
Common Use Cases
- Tire Warranties: Tire manufacturers often offer pro rata warranties. If a tire rated for 50,000 miles fails at 25,000 miles, you may receive a 50% credit toward a replacement.
- Car Batteries: Batteries usually have a "free replacement" period followed by a "pro rata" period. During the pro rata phase, you pay a portion of the new battery's cost based on how old the failed battery is.
- Property Insurance: In Actual Cash Value (ACV) policies, insurers deduct depreciation from the replacement cost of a damaged item based on its age and condition.
Example Calculation
Let's say you purchased a car battery for $200 with a 50-month warranty. The battery fails after 20 months.
- Total Life: 50 months
- Time Used: 20 months
- Remaining Life: 30 months (50 – 20)
- Calculation: $200 × (30 / 50) = $200 × 0.60 = $120
In this scenario, you would receive a $120 credit towards a new battery, or you would be responsible for $80 of depreciation.
FAQ
What happens if I use the product longer than the warranty period?
If the "Time Used" is greater than or equal to the "Total Warranty/Life Expectancy," the depreciation reaches 100%. In this case, the refund value is $0, as the product has fulfilled its expected lifespan.
Does this calculator account for inflation?
No, this calculator uses the standard linear pro rata method based on the original purchase price. It does not account for the current market price of a replacement item, though some specific warranty contracts may be based on the "current list price" rather than the original price.
Why is my refund lower than expected?
Some vendors calculate pro rata credits based on the current retail price rather than what you originally paid. If the price has gone up, this benefits you; if it has gone down, your credit might be smaller. Always check the specific terms of your warranty document.