Blended Rate Mortgage Calculator
Carrying a first mortgage plus a second mortgage or HELOC? Your true borrowing cost is not either rate — it is the weighted blend of both. Enter your balances and rates to find the single blended rate that applies to your combined home debt.
How the blended mortgage rate formula works
A blended mortgage rate weights each loan's interest rate by its balance, so a large first mortgage counts for more than a smaller second lien:
Example: a $300,000 first mortgage at 6.25% combined with a $50,000 HELOC at 8.50% works out to (300,000 × 6.25 + 50,000 × 8.50) ÷ 350,000 = 6.57% blended. The simple average of the two rates (7.38%) overstates your real cost because the HELOC is a small fraction of the total balance.
When homeowners need this number
- Cash-out refinance decisions — a single new loan only saves money if its rate beats your current blended rate.
- Piggyback (80/10/10) loans — see the effective rate of a first mortgage plus a second used to avoid PMI, and compare it against one 90% LTV loan with PMI.
- Mortgage + HELOC households — track how each HELOC rate reset moves your total cost of borrowing.
- Second mortgage vs. refinance — check whether adding a second lien keeps your blended rate below today's refinance rates before giving up a low first-mortgage rate.
Learn more about blended mortgage rates
- Mortgage + HELOC blended rate — the break-even math before a cash-out refinance.
- First and second mortgage combined rate — your true home-loan cost across both liens.
- Blend and extend mortgage — mix your old rate with today's and reset the term.
- Piggyback (80/10/10) vs PMI — when a second mortgage beats mortgage insurance.
- Variable vs fixed HELOC — protecting your blend from rate resets.
Frequently asked questions
What is a blended mortgage rate?
A blended mortgage rate is the weighted average interest rate across two or more home loans — typically a first mortgage plus a second mortgage or HELOC. Each loan's rate is weighted by its balance, so the result reflects what your combined home debt actually costs.
How do you calculate a blended mortgage rate?
Multiply each loan's balance by its interest rate, add those products together, then divide by your total combined balance. For example, $300,000 at 6.25% plus $50,000 at 8.50% gives a blended rate of 6.57% — not the 7.38% simple average.
Why does my blended rate matter when refinancing?
Your blended rate is the benchmark a cash-out refinance offer has to beat. If a lender offers you one new loan at a rate above your current blended rate, consolidating your mortgage and HELOC would increase your interest cost, not lower it.
Should I include my HELOC at its current variable rate?
Yes — use today's rate. Because HELOC rates move with the prime rate, your blended rate changes whenever your HELOC rate resets, so recalculate after each rate change before making refinancing decisions.
Does the blended rate account for different loan terms?
No. The blended rate is a snapshot of your current interest cost and ignores how long each loan runs. Two loans with the same blended rate but different terms can have very different lifetime interest costs, so also compare total interest when weighing a refinance.
Blending more than home loans?
Combine up to four loans of any type — mortgage, auto, student, personal — to find the weighted average rate on all of your debt.