Assumptions
- The extra amount is paid every month until the debt reaches zero.
- The balance, APR, and normal payment are identical in both plans.
- The extra payment does not cause fees or change the APR.
Extra payment calculator
See how much sooner an extra payment reaches $0
An extra monthly payment changes both the payoff timeline and the interest charged along the way. Compare your current payment with one specific added amount to measure the difference without changing the original plan.
Private by design
Your financial values stay in this browser.
No account required
No signup, bank connection, or credit pull.
Deterministic math
The same inputs produce the same estimate.
Calculate locally
Compare without and with an extra payment
Enter your current balance, APR, normal monthly payment, and the additional amount you want to test.
Extra payment calculator
Compare without extra and with extra
The extra amount is added to your current monthly payment for every simulated month.
Understand the output
The impact of your extra payment
The comparison keeps your balance and APR fixed, then reports both payoff dates, months saved, interest saved, and the new total paid.
Methodology and limits
How this calculator estimates payoff
The baseline uses the current monthly payment. The comparison adds the entered extra amount to that payment every modeled month.
Both plans run through the same monthly interest, cent-rounding, final-payment, and 100-year safety rules.
Limitations
- The comparison does not test whether the added amount is affordable.
- Actual savings can differ because of lender accrual and payment-posting rules.
Methodology reviewed August 26, 2026. Results are educational planning estimates, not financial advice or lender payoff quotes.
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