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;
}
.calculator-container {
background-color: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 25px;
margin-bottom: 30px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.calc-header {
text-align: center;
margin-bottom: 25px;
}
.calc-header h2 {
margin: 0 0 10px 0;
color: #2c3e50;
}
.input-group {
margin-bottom: 20px;
padding-bottom: 15px;
border-bottom: 1px dashed #ced4da;
}
.input-group:last-of-type {
border-bottom: none;
}
.input-row {
display: flex;
gap: 15px;
margin-bottom: 10px;
}
.input-col {
flex: 1;
}
.input-col label {
display: block;
font-size: 0.9em;
font-weight: 600;
margin-bottom: 5px;
color: #495057;
}
.input-col input {
width: 100%;
padding: 10px;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 16px;
}
.input-col input:focus {
border-color: #4facfe;
outline: none;
box-shadow: 0 0 0 3px rgba(79, 172, 254, 0.2);
}
button.calc-btn {
display: block;
width: 100%;
background: linear-gradient(to right, #4facfe 0%, #00f2fe 100%);
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 6px;
cursor: pointer;
transition: transform 0.1s;
}
button.calc-btn:hover {
opacity: 0.95;
transform: translateY(-1px);
}
#results-area {
margin-top: 25px;
background: white;
padding: 20px;
border-radius: 6px;
border: 1px solid #dee2e6;
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
margin-bottom: 10px;
font-size: 1.1em;
}
.result-row.highlight {
font-weight: bold;
color: #2c3e50;
font-size: 1.4em;
border-top: 2px solid #eee;
padding-top: 10px;
margin-top: 10px;
}
.article-content h2 {
color: #2c3e50;
margin-top: 30px;
}
.article-content h3 {
color: #34495e;
}
.excel-box {
background-color: #f1f8e9;
border-left: 5px solid #8bc34a;
padding: 15px;
font-family: monospace;
margin: 15px 0;
overflow-x: auto;
}
@media (max-width: 600px) {
.input-row {
flex-direction: column;
gap: 10px;
}
}
function calculateBlendedRate() {
// Get Inputs for Loan 1
var b1 = parseFloat(document.getElementById('balance1').value);
var r1 = parseFloat(document.getElementById('rate1').value);
// Get Inputs for Loan 2
var b2 = parseFloat(document.getElementById('balance2').value);
var r2 = parseFloat(document.getElementById('rate2').value);
// Get Inputs for Loan 3
var b3 = parseFloat(document.getElementById('balance3').value);
var r3 = parseFloat(document.getElementById('rate3').value);
// Validation / Defaulting
if (isNaN(b1)) b1 = 0;
if (isNaN(r1)) r1 = 0;
if (isNaN(b2)) b2 = 0;
if (isNaN(r2)) r2 = 0;
if (isNaN(b3)) b3 = 0;
if (isNaN(r3)) r3 = 0;
// Calculate Total Principal
var totalPrincipal = b1 + b2 + b3;
if (totalPrincipal === 0) {
alert("Please enter at least one loan balance.");
return;
}
// Calculate Weighted Interest
// (Balance * Rate) gives the weighted portion
var w1 = b1 * r1;
var w2 = b2 * r2;
var w3 = b3 * r3;
var totalWeighted = w1 + w2 + w3;
// Blended Rate Formula: Sum(Balance * Rate) / Sum(Balance)
var blendedRate = totalWeighted / totalPrincipal;
// Annual Interest Cost (Absolute Dollars)
// Rate is in percentage, so divide by 100 for dollar calc
var annualCost = (totalWeighted / 100);
// Update UI
document.getElementById('res-total-debt').innerText = '$' + totalPrincipal.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-total-interest').innerText = '$' + annualCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-blended-rate').innerText = blendedRate.toFixed(3) + '%';
// Show results
document.getElementById('results-area').style.display = 'block';
}
How to Calculate a Blended Rate: Excel Guide & Formula
A blended rate is the weighted average interest rate across multiple loans or debt vehicles. It is a critical metric for real estate investors using "Subject To" financing, homeowners considering a Home Equity Line of Credit (HELOC) versus a full refinance, and businesses consolidating debt.
Unlike a simple average, which treats all loans equally, a blended rate accounts for the fact that a larger loan balance has a greater impact on your overall interest costs than a smaller balance.
The Mathematical Formula
To calculate a blended rate manually, you follow these three steps:
- Multiply each loan balance by its specific interest rate to get the "weighted interest" factor.
- Add all the weighted interest factors together.
- Divide that sum by the total balance of all loans combined.
Formula = [(Balance1 × Rate1) + (Balance2 × Rate2)] / (Total Balance)
How to Calculate a Blended Rate in Excel
Excel is the most efficient tool for this calculation, especially if you have more than two loans. You can use the SUMPRODUCT function to automate the math.
Step 1: Setup Your Columns
Create two columns in Excel:
- Column A: Loan Balances (e.g., A2:A5)
- Column B: Interest Rates (e.g., B2:B5) (Format these cells as percentages)
Step 2: The Formula
In a new cell, enter the following formula:
=SUMPRODUCT(A2:A5, B2:B5) / SUM(A2:A5)
Step 3: Interpretation
The SUMPRODUCT function multiplies each balance by its corresponding rate and adds them up (the numerator). The SUM function calculates the total debt load (the denominator). Dividing the two gives you the true weighted blended rate.
Real-World Example
Imagine you have a primary mortgage and you want to take out a second mortgage (HELOC) for renovations. You want to know if keeping your low-rate primary mortgage and adding a higher-rate HELOC is cheaper than refinancing the entire amount at current market rates.
- Loan 1 (Primary): $300,000 at 3.0%
- Loan 2 (HELOC): $50,000 at 9.0%
Using the calculator above or the Excel formula:
Numerator: (300,000 × 3.0) + (50,000 × 9.0) = 900,000 + 450,000 = 1,350,000
Denominator: 300,000 + 50,000 = 350,000
Result: 1,350,000 / 350,000 = 3.857%
Your blended rate is roughly 3.86%. If the current refinance rate for a single loan is 6.5%, you are significantly better off keeping the two separate loans.
Why Not Just Average the Rates?
If you simply averaged 3.0% and 9.0%, you would get 6.0%. This is incorrect because the vast majority of your debt ($300k vs $50k) is held at the lower rate. The blended rate accurately reflects that the 3.0% rate carries more "weight" in your financial picture.