First and Second Mortgage Combined Rate: Finding Your True Home-Loan Cost

Once you hold a first and a second mortgage — whether from a piggyback purchase, a later home equity loan, or a HELOC — you no longer have "a mortgage rate." You have two, and the only number that tells you your real cost of borrowing against the house is the combined, blended rate.

Your combined first-and-second mortgage rate is the balance-weighted average of both loans: multiply each balance by its rate, add them, and divide by the total. That single blended rate is what any cash-out refinance offer must beat to actually save you money. Comparing a refinance only to your second mortgage's higher rate is how people talk themselves into losing deals.

Blend your two mortgages here:

Why the Combined Rate Matters

Second mortgages and HELOCs carry higher rates than firsts because they sit behind the first in line if you default. So your second might be at 8.5% while your first is at 3.5%. If a lender offers a 6% cash-out refinance, the 6% looks great next to 8.5% — but it's worse than your blend if the first mortgage is large.

Combined Rate = (First Balance × First Rate + Second Balance × Second Rate) / Total Balance

Worked Example

Combined rate = $16,300 ÷ $380,000 = 4.29%. A 6% refinance that "beats" the 8.5% second mortgage would actually raise your true cost from 4.29% to 6% — a costly mistake driven by looking at the wrong number.

When Refinancing Both Does Make Sense

• Your first mortgage rate is already at or above current market rates.
• The combined rate is genuinely high because both loans are expensive.
• You want to eliminate a variable-rate second whose rate keeps climbing — see variable vs fixed HELOC.
• You need to consolidate for cash flow, accepting a higher rate knowingly.

For the fuller mortgage-plus-HELOC decision, including break-even math, see mortgage + HELOC blended rate.

Frequently Asked Questions

How do I calculate the combined rate on a first and second mortgage?

Multiply each mortgage's balance by its interest rate, add the two results, and divide by the total balance of both loans. The result is your blended combined rate — a weighted average that reflects how much of your debt sits at each rate.

Why is my second mortgage rate higher than my first?

Second mortgages and HELOCs are subordinate — if you default and the home is sold, the first mortgage is repaid before the second. That added risk to the lender is priced in as a higher interest rate on the second loan.

Should I refinance to get rid of my second mortgage?

Only if the refinance rate beats your combined (blended) rate, not just your second mortgage's rate. If your first mortgage carries a low rate on a large balance, refinancing everything can raise your true cost. Consider refinancing only the second mortgage instead.

Does a HELOC count as a second mortgage for the combined rate?

Yes. A HELOC is a form of second lien on your home, so include its balance and current rate in the combined-rate calculation exactly like a fixed second mortgage. Because HELOC rates are usually variable, recalculate the blend whenever the rate resets.