Blend and Extend Mortgage: How the Rate Is Calculated (With Calculator)
A blend-and-extend blends your current mortgage rate with today's market rate to reset your term. Learn how the calculation works and when it pays off.
Blended Rate Calculator
Know exactly what your debt costs. Add as many balances and rates as you need to find your true weighted average interest rate β and see exactly what your combined loans cost you every month.
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How it works
Follow three interactive steps to calculate your true weighted average interest rate.
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Base Tranche (Primary Loan)
Your primary mortgage or largest loan sets the foundation weight. Tap preset numbers to see how debt accruals update in real-time:
Loan 1 Balance$300,000
Annual Interest Rate6.50%
Annual Interest$19,500/yr
Monthly Interest$1,625/mo
Foundation Rule: This tranche is required because it establishes the baseline balance. All other loans blend into this anchor.
How the Math Actually Works
Your blended rate is the mathematical reality of your combined debt. Each loan's rate is weighted by its balance. If you simply average a $300,000 mortgage and a $20,000 HELOC, the small loan distorts the picture and the result misstates your true cost. The blended rate gives you the single, accurate interest rate that applies to your total outstanding balance. Always check this number before you consolidate or refinance.
Blended Rate = Ξ£(Balance Γ Rate) / Ξ£(Balance)Step 1 β Multiply balance by rate
($300,000 Γ 6.5%) = 1,950,000
($75,000 Γ 7.75%) = 581,250
Step 2 β Sum the products
1,950,000 + 581,250 = 2,531,250
Step 3 β Divide by total balance
2,531,250 Γ· $375,000 = 6.750%
The blended rate is 6.750%, not the simple average of 7.125%.
Worked examples
| Scenario | Calculation | Result |
|---|---|---|
| First mortgage + HELOC | Loan A: $320,000 @ 6.25% Β· Loan B: $50,000 @ 8.50% | 6.55% blended |
| Two student loans at different rates | Loan A: $18,500 @ 5.05% Β· Loan B: $12,000 @ 6.80% | 5.74% blended |
| First mortgage + second mortgage | Loan A: $280,000 @ 5.875% Β· Loan B: $65,000 @ 7.25% | 6.13% blended |
| Three personal loans consolidated | Loan A: $15,000 @ 9.99% Β· Loan B: $8,500 @ 12.50% Β· Loan C: $4,000 @ 18.00% | 11.93% blended |
| Single loan (edge case) | Loan A: $200,000 @ 7.00% | 7.00% blended |
Conversion reference
| Loan Type | Typical Rate Range |
|---|---|
| 30-year fixed mortgage | 6.25% β 6.75% |
| 15-year fixed mortgage | 5.50% β 6.25% |
| Home equity line of credit (HELOC) | 7.00% β 8.25% |
| Federal student loan (undergraduate) | 5.50% β 6.55% (recent loan cohorts) |
| Personal loan | 10.00% β 28.00% |
Quick facts
- Total US mortgage debt exceeded $12.5 trillion in 2024, making the blended rate the most practical way for homeowners with multiple liens to measure their true borrowing cost. (Federal Reserve Flow of Funds, 2024)
- Roughly 13% of US homeowners carried a home equity line of credit in 2023, with average outstanding HELOC balances near $42,000 β making the first-mortgage-plus-HELOC blended rate one of the most common calculations homeowners need. (Federal Reserve Survey of Consumer Finances, 2022)
- The average American household carrying debt holds approximately $104,215 in total obligations, including mortgage, auto, student loans, and credit cards. Without a blended rate, it is nearly impossible to assess whether a consolidation offer represents real savings. (Experian State of Credit, 2023)
See This Calculator in Action
Real-world case studies showing how borrowers use the Blended Rate Calculator to make smarter financial decisions.
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Frequently asked questions
Your blended rate is the true, weighted average interest rate across all your loans. It proves exactly what your combined debt costs you. If you applied this single rate to your total debt balance, you would pay the exact same amount in interest as your current messy mix of loans.
This blended interest rate calculator takes the balance and rate of each of your loans, multiplies every balance by its rate, adds those results together, and divides by your total balance. That weighted-average math returns one blended interest rate for your whole portfolio in real time as you type β no sign-up, and nothing you enter leaves your device.
Because a simple average is misleading. It treats a $300,000 mortgage at 3% and a $5,000 credit card at 25% as equals. A blended rate weights each loan by its actual balance, giving you an accurate picture of where your money is going.
Use it every time a lender offers to refinance or consolidate your debt. If the new loan's rate is higher than your current blended rate, the offer costs you more β not less. Run the numbers here before you sign anything.
No. The blended rate only uses your stated interest rates. If you want to see how much origination fees and closing costs add to a loan's true cost, calculate the APR (Annual Percentage Rate) using our APR Calculator.
Enter your mortgage balance and rate as Loan 1. Enter your HELOC balance and rate as Loan 2. If your HELOC is variable, use today's rate. When the Fed moves rates and your HELOC jumps, recalculate it.
Maybe. If a lender offers a consolidation loan at a rate lower than your blended rate, you will save money. But watch out for the trap: if they stretch out your repayment timeline to 7 years, you might get a lower monthly payment but end up paying thousands more in total interest. Always check the total interest cost.
It depends on the market, but as a rule: if your blended rate is lower than the current 30-year fixed mortgage rate, you are in good shape. If it's creeping toward 10% because of credit cards or personal loans, you are paying significantly more than you need to, and consolidation is worth exploring.
Yes. Enter each student loan as a separate line item. If you have eight tiny loans, average a few of them together to fit them into the four slots. This is the exact math you need before doing a Federal Direct Consolidation, which rounds up your rate.
No, this uses simple interest math. Most mortgages and student loans compound monthly, so your effective annual cost is slightly higher than the stated rate. But for comparing your current debt against a refinance offer, simple interest gives you the perfect baseline.
Absolutely not. APR (Annual Percentage Rate) is a legally required number that includes hidden fees and points for a single new loan. Blended rate is the weighted average of the loans you already have. Use blended rate to see what you pay today; use APR to see what a new loan will cost you tomorrow.
Use whatever the rate is today. If you have a variable HELOC or an adjustable-rate mortgage (ARM), your blended rate is going to change every time your lender changes your rate. Recalculate it every time you get a new statement.
Not directly. The blended rate tells you what your current portfolio of debt costs. To compare two lenders, use APR β it is the legally standardized number that includes fees. But once you know your current blended rate, you have a benchmark: any consolidation offer with an APR above that number is not worth taking.
Enter your first mortgage balance and rate as Loan 1. Enter your second mortgage (or HELOC) balance and rate as Loan 2. The calculator will weight each by its balance and give you the true combined rate. This is the number to use when a lender pitches you a cash-out refinance β if their rate is higher than your blended rate, walk away.
They are the same thing. Blended rate and weighted average interest rate are two names for an identical calculation. The term 'blended rate' is more common in consumer finance and mortgages; 'weighted average rate' is more common in corporate finance and bond portfolios. The formula is identical: sum of (balance Γ rate) divided by total balance.
Recalculate whenever something changes: a variable rate adjusts, you make a large extra payment, you take on a new loan, or a lender approaches you with a consolidation offer. For most people with fixed-rate loans, once per year at tax time is enough. If you carry a variable-rate HELOC, check it every time the Fed makes a rate decision.