Enter up to 5 items with their individual rates and corresponding weights (amounts).
Item 1:
Item 2:
Item 3:
Item 4:
Item 5:
Weighted Average Rate
0.00%
Total Weight/Amount: 0
function calculateWeightedRate() {
var totalWeightedSum = 0;
var totalWeight = 0;
var hasValidInput = false;
// Helper function to safely get number values
function getNumValue(id) {
var val = parseFloat(document.getElementById(id).value);
return isNaN(val) ? 0 : val;
}
// Loop through 5 possible inputs
for (var i = 1; i 0) {
totalWeightedSum += (rate * weight);
totalWeight += weight;
hasValidInput = true;
}
}
var resultDiv = document.getElementById('wrc-result');
var finalRateSpan = document.getElementById('wrc-final-rate');
var totalWeightSpan = document.getElementById('wrc-total-weight');
if (hasValidInput && totalWeight > 0) {
var weightedAverage = totalWeightedSum / totalWeight;
finalRateSpan.innerText = weightedAverage.toFixed(3) + "%";
// Format total weight with commas if it's a large number
totalWeightSpan.innerText = totalWeight.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 2});
resultDiv.style.display = 'block';
} else {
// Handle edge case where no valid weights are entered
finalRateSpan.innerText = "Cannot calculate";
totalWeightSpan.innerText = "0 (Please enter at least one weight greater than zero)";
resultDiv.style.display = 'block';
}
}
Understanding the Weighted Rate Calculator
A weighted rate calculator determines the average value of a dataset where certain items contribute more to the final average than others. This is known as a "weighted average" or "weighted mean." Unlike a standard simple average, where every number counts equally, a weighted average assigns a specific "weight" (importance or volume) to each number.
When to Use a Weighted Average Calculator
You should use a weighted average whenever the components of your average have different levels of importance or different underlying volumes. Common scenarios include:
Finance (Blended Rates): Calculating the overall interest rate on multiple debts (like a mortgage combined with a HELOC) where the loan balances differ significantly.
Investing: Determining the average return percentage of a portfolio where different amounts of capital are invested in different assets.
Inventory Accounting: Calculating the average cost per unit of inventory purchased at different prices and different quantities over time.
Education: Calculating Grade Point Average (GPA), where some classes are worth more credits than others.
The Weighted Rate Formula
The mathematics behind this calculator is relatively straightforward. The formula for a weighted average is:
Weighted Average = Σ (Rate × Weight) / Σ (Weight)
In simpler terms:
Multiply each item's Rate by its corresponding Weight.
Add up all of those results (this is the sum of the weighted values).
Add up all the Weights individually (this is the total weight).
Divide the sum from step 2 by the total weight from step 3.
Example Calculation: Blended Interest Rate
Let's say you are trying to figure out the "blended" interest rate of two different debts:
Debt A: $200,000 at a 4.5% rate.
Debt B: $50,000 at a 9.0% rate.
If you just averaged the rates (4.5% + 9.0%) / 2, you would get 6.75%. This is incorrect because Debt A is much larger than Debt B. A weighted average is necessary.