| Year | Total Paid | Interest | Principal | Extra Principal | Ending Balance |
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This calculator estimates principal and interest only. Taxes, insurance, PMI, HOA dues, and lender-specific rules are not included.
Why an amortization calculator with extra payments matters
A standard mortgage amortization schedule assumes you make the same required payment every month for the full loan term. But real life is rarely that tidy. Many homeowners pay a little extra toward principal each month, throw in a bonus payment once a year, or make occasional lump-sum prepayments. This calculator helps you model those choices and see the potential impact on payoff time and total interest.
How mortgage amortization works
With a fixed-rate mortgage, your monthly principal-and-interest payment is typically constant. Early in the loan, a larger share of each payment goes to interest. As the balance falls, less interest accrues each month, and more of your payment goes to principal.
Simple breakdown
- Interest is based on your current remaining loan balance.
- Scheduled principal is whatever is left from your monthly payment after interest.
- Extra payments directly reduce principal (if applied correctly by your servicer).
How extra mortgage payments help
Extra payments reduce principal sooner, which means less interest is charged in future months. Even modest additional principal payments can compound into meaningful savings over time.
Common extra payment strategies
- Monthly extra principal: Add a fixed amount to every payment.
- Annual lump sum: Use tax refunds or bonuses for one extra principal hit per year.
- One-time prepayment: Apply a large windfall once (inheritance, asset sale, etc.).
How to use this calculator
- Enter your mortgage amount, APR, term, and start date.
- Add your planned extra monthly, annual, and one-time payments.
- Click Calculate Amortization.
- Review your new payoff date, time saved, and estimated interest savings.
What to check before prepaying your mortgage
- Confirm your lender applies extra funds to principal, not future interest.
- Make sure there is no prepayment penalty.
- Compare mortgage prepayment versus higher-interest debt payoff.
- Keep an emergency fund so extra payments do not hurt cash flow.
- Consider opportunity cost (retirement contributions, investing, business growth).
FAQ
Will a small extra payment really make a difference?
Yes. Because interest is calculated on remaining balance, even a small recurring extra principal payment can shorten the loan and reduce total interest.
Should I make biweekly payments instead?
Biweekly plans can help, especially if they create the equivalent of one extra monthly payment per year. This calculator uses monthly modeling, but you can approximate biweekly impact by increasing your monthly extra principal amount.
Is paying off a mortgage early always best?
Not always. It depends on your interest rate, risk tolerance, liquidity needs, tax situation, and alternative returns. Use this as a planning tool, then make a balanced financial decision.