15-Year Mortgage Extra Payment Calculator
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Reviewed by Calculator Editorial Team
This calculator helps you determine how making extra payments on a 15-year mortgage affects your interest savings, payoff date, and total interest paid. Whether you're looking to pay off your mortgage faster or reduce your interest costs, this tool provides clear insights into the impact of your extra payments.
How the Calculator Works
The 15-year mortgage extra payment calculator uses standard amortization formulas to project the impact of your extra payments. Here's how it works:
Amortization Formula
The monthly payment (P) for a mortgage is calculated using the formula:
P = (L × r × (1 + r)^n) / ((1 + r)^n - 1)
Where:
- L = Loan amount
- r = Monthly interest rate (annual rate ÷ 12)
- n = Total number of payments (loan term in years × 12)
The calculator then applies your extra payments to the principal balance each month, reducing the total interest paid and accelerating the payoff date. The results show the new payoff date, total interest saved, and how the extra payments affect your monthly payments.
Key Assumptions
The calculator assumes:
- Fixed interest rate throughout the loan term
- Extra payments are applied to the principal first
- No prepayment penalties
- Monthly compounding of interest
How to Use This Calculator
- Enter your current mortgage details in the calculator panel on the right.
- Specify the amount of your extra monthly payment.
- Click "Calculate" to see the impact of your extra payments.
- Review the results, including the new payoff date, interest savings, and adjusted monthly payments.
- Use the chart to visualize how your extra payments reduce the principal balance over time.
Example Calculation
Let's say you have a $200,000 15-year mortgage with a 4% annual interest rate. Your standard monthly payment would be approximately $1,520. If you make an extra $200 each month, here's what the calculator would show:
| Metric | Standard Mortgage | With Extra Payments |
|---|---|---|
| Payoff Date | December 2035 | June 2033 |
| Total Interest Paid | $120,000 | $96,000 |
| Interest Saved | $24,000 | |
| Monthly Payment | $1,520 | $1,720 |
In this example, making extra payments saves you $24,000 in interest and pays off your mortgage 2 years early.
Frequently Asked Questions
How do extra payments affect my monthly payments?
Making extra payments typically increases your monthly payments because you're paying more toward principal, which reduces the total interest you'll pay over the life of the loan. However, the calculator shows the exact impact on your monthly payments and interest savings.
Can I make extra payments at any time?
Yes, the calculator assumes you make extra payments each month. However, in reality, you might make lump-sum payments occasionally. The results will be slightly different in those cases, but the calculator provides a good approximation.
Will making extra payments save me money?
Yes, making extra payments on a 15-year mortgage can save you thousands in interest over the life of the loan. The calculator shows exactly how much you'll save by making extra payments.
How does the interest rate affect the results?
A higher interest rate means you'll pay more interest over the life of the loan. The calculator accounts for your current interest rate and shows how extra payments can reduce the total interest paid.