Extra-payment calculator
See how paying extra could help you repay your loan sooner.
Interest is the cost of borrowing money. Paying extra reduces what you owe, so you could pay less interest and finish repaying sooner.
For an existing loan with a fixed interest rate and monthly payments. You’ll need three numbers from your loan statement.
Enter your loan details, then select “See the difference”.
What could change for you
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All amounts use the same currency as your loan. These estimates may differ from your lender’s figures.
Watch the amount you owe go down
Compare all the numbers
Estimate: a fixed yearly interest rate, divided by 12. Interest is rounded half-up to two decimal places each month. Payments happen at month end: usual payment, then monthly extra, then one-time extra. No fees, taxes, insurance or penalties are included. This is not a lender payoff quote or a recommendation.
Explore or save a payment breakdown
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Monthly payment breakdown
How extra payments can help
Part of each loan payment covers interest. The rest reduces the amount you owe. An extra payment reduces that amount further, which can lower future interest. This calculator keeps your usual monthly payment the same.
Before paying extra, check whether your lender charges a fee and how it handles extra payments. The estimate here uses a fixed interest rate and monthly payments; your lender’s rules may differ.
How we calculate this
A monthly estimate
Each month, interest equals the opening balance × annual nominal rate ÷ 100 ÷ 12, rounded half-up to the nearest hundredth of a currency unit. The annual nominal rate is the yearly interest rate before the effect of interest building up, not regulatory APR. We add that interest, apply your usual payment, then the monthly extra and any one-time extra payment. The remainder is next month’s opening balance.
A worked example
For example, a balance of 1,000 at 12% accrues 10.00 interest in month 1. A usual payment of 100 reduces the amount owed to 910.00; a further 50 reduces it to 860.00. With monthly rounding, that loan takes 11 payments and 58.98 interest without extras, or 7 payments and 40.12 interest with an extra 50 every month. That is 4 months sooner and 18.86 less interest.
Limits of this estimate
Each actual payment stops at the amount needed to repay the loan. We stop at zero and report any unused one-time extra payment. Your usual payment must cover more than the first month’s rounded interest, and must repay the loan within 50 years (600 monthly payments). Money accepts up to two decimal places; the yearly rate accepts up to six, between 0 and 100%. Amounts are limited to 1,000,000,000 units. Positive loan amounts and usual payments start at 0.01; monthly extras can be zero.
This model excludes variable rates, daily interest, escrow, taxes, insurance, fees, early-payment penalties, recasting (changing the usual payment after an extra payment) and refinancing (replacing the loan). It does not estimate calendar payoff dates. Lender rounding and payment rules may differ. Use one currency with hundredth-unit precision throughout.
For more on how payments reduce a loan, see the CFPB’s payment explanation. Its mortgage examples do not define this calculator’s rules for every country or lender.
Model version: monthly-rounded-v1. No account, saved options or automatic sharing.