Amortization Calculator with Extra Payments
Break a fixed loan payment into principal and interest and compare the payoff timeline with an optional extra payment.
Quick answer
Enter the current balance, fixed APR, remaining term, and optional extra principal. Results show the scheduled payment, first-payment split, estimated interest, and payoff time.
Formula used
The scheduled payment uses the standard amortization formula. Each month, interest equals the remaining balance × APR ÷ 12; the rest of the payment reduces principal.
Worked example
On a long-term loan, the first payments usually contain more interest because the balance is largest. Extra principal reduces the balance used for future interest calculations.
How to interpret the result
Use the comparison to test scenarios, then verify important decisions against current account documents and provider rules. A calculator is most useful when the inputs match the balance, rate, payment timing, and fees that apply to you.
Limitations
This is a monthly estimate. It excludes escrow, taxes, insurance, fees, changing rates, late payments, and lender-specific rules. It is not an official payoff quote.
Source and methodology
CFPB explanation of loan estimates and payments. The source supports the general concept; ToolGemini performs the calculation locally from the values you enter and the formula described above.
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Frequently asked questions
What is amortization?
Amortization is the process of paying a balance over time through scheduled payments that include both principal and interest.
Why is more interest paid near the beginning?
Interest is calculated from the outstanding balance. The balance is normally highest at the start, so the interest portion is also larger.
How are extra payments modeled?
The entered extra amount is added to every monthly payment and assumed to reduce principal immediately. Confirm application rules with the lender.