Second Mortgage Calculator
Estimate the fixed monthly payment and total interest on a second mortgage, and see your resulting combined loan-to-value.
How the second mortgage calculator works
A second mortgage is a fixed-rate loan that sits behind your existing first mortgage as a junior lien on the same home. You receive a lump sum, repay it on its own term and rate, and the lender's claim ranks below the first mortgage if the property is ever sold or foreclosed.
Borrowers use it to tap built-up equity or to avoid private mortgage insurance on a purchase. This calculator computes the second loan's payment and total interest, then frames it against your first balance so the combined loan-to-value picture is visible.
Worked example: with home value of $450,000, first mortgage balance of $260,000 and second mortgage amount of $60,000, the second mortgage calculator shows second mortgage payment of $590.84.
- Monthly payment
- $590.84
- Total interest
- $46,352
- Total of payments
- $106,352
- Combined LTV
- 71.1%
| Second mortgage amount | Second mortgage payment |
|---|---|
| $25,000 | $246.18 |
| $50,000 | $492.37 |
| $100,000 | $984.74 |
| $150,000 | $1,477.11 |
The formula
The monthly payment uses the standard amortization formula on the second loan's balance, rate, and term, independent of the first mortgage. Total interest is the payment times the number of payments minus the principal. Combined loan-to-value equals both mortgage balances added together, divided by the home's value.
- The second loan is treated as a fixed-rate, fully amortizing lump sum, not a revolving HELOC whose balance and payment fluctuate.
- It carries its own rate and term, usually higher than the first mortgage because the junior lien position is riskier for the lender.
- Combined loan-to-value uses an assumed home value; an appraisal at application may differ and change how much you can borrow.
- The first mortgage payment is not added here; budget for both liens together when judging affordability.
- Taxes, insurance, and closing costs on the second loan are excluded, and a fixed rate with on-time payments is assumed.
Results are estimates for educational purposes and are not financial advice. Confirm exact figures with your lender or a licensed advisor.
Questions about the second mortgage calculator
How is a second mortgage different from a HELOC?
Structure. A second mortgage, often called a home equity loan, hands you a single lump sum at a fixed rate with set monthly payments, much like your first mortgage.
A HELOC is a revolving line you draw from as needed, usually at a variable rate, with payments that move as the balance and rate change. This calculator models the fixed lump-sum version.
Why is the rate on a second mortgage higher than my first?
Lien position. If the home is sold or foreclosed, the first mortgage is repaid in full before the second lender sees a dollar, so the second loan carries more risk of loss. Lenders price that risk into a higher rate.
The same logic explains why second mortgages often have shorter terms and stricter equity requirements than the primary loan sitting ahead of them.
What does combined loan-to-value mean and why does it matter?
Combined loan-to-value adds your first and second mortgage balances together and divides by the home's value. Lenders cap it — often around 80 to 85 percent — because the more you borrow against the home, the less cushion remains if values fall.
A lower combined ratio improves your odds of approval and your rate, and it leaves more equity protected should you need to sell.
Is the Second Mortgage Calculator free to use?
Yes. Every calculator on MortgageLoansCalculator is completely free, with no sign-up, login or paywall. Run as many scenarios as you like.
What is a second mortgage?
A second mortgage is a loan against your home equity that sits behind your first mortgage — usually a home equity loan or HELOC.
It adds a payment on top of your first loan, and lenders cap the two together at a combined loan-to-value around 80–85%.
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