15 Year Second Mortgage Calculator with Extra Payments
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Reviewed by Calculator Editorial Team
This 15-year second mortgage calculator helps you determine your monthly payments when you take out a second mortgage and make extra payments. It calculates the principal and interest payments, total interest paid, and how extra payments reduce your loan term and interest costs.
How This Calculator Works
The calculator uses the standard mortgage payment formula to determine your monthly payments, then applies your extra payments to show how they affect your loan term and interest costs. The formula accounts for:
- The loan amount (principal)
- The interest rate
- The loan term (15 years)
- Any extra payments you make each month
The calculator shows you the monthly payment, total interest paid, and how long it will take to pay off the loan with your extra payments. It also provides a chart showing the loan balance over time.
How to Use This Calculator
- Enter the loan amount for your second mortgage.
- Enter the interest rate (APR).
- Enter any extra payments you plan to make each month.
- Click "Calculate" to see your results.
- Review the monthly payment, total interest paid, and loan term with extra payments.
- Use the chart to visualize how your loan balance decreases over time.
Note: This calculator assumes you make the same extra payment each month. If you plan to make irregular extra payments, the results may vary.
Example Calculation
Let's say you take out a $100,000 second mortgage at 4.5% APR for 15 years. If you make an extra $200 payment each month, here's what the calculator would show:
| Metric | Without Extra Payments | With $200 Extra Payments |
|---|---|---|
| Monthly Payment | $743.65 | $943.65 |
| Total Interest Paid | $126,182.40 | $82,560.20 |
| Loan Term | 15 years | 12 years and 6 months |
In this example, making extra payments saves you $43,622.20 in interest and reduces your loan term by 2 years and 6 months.
Formula Used
The calculator uses the following formula to determine monthly payments:
Monthly Payment = P * (r(1 + r)^n) / ((1 + r)^n - 1)
Where:
- P = Principal loan amount
- r = Monthly interest rate (APR/12)
- n = Number of payments (loan term in months)
For extra payments, the calculator applies each payment to the principal first, then calculates the remaining interest payment.
Frequently Asked Questions
This calculator provides an estimate based on standard mortgage formulas. For precise figures, consult with your lender or use their exact calculations.
This calculator is specifically designed for second mortgages. For first mortgages, use our dedicated first mortgage calculator.
The calculator assumes regular extra payments. For irregular payments, you may need to adjust the results manually.
Making extra payments can improve your credit score by reducing your credit utilization ratio and demonstrating responsible debt management.