Amortization Calculator

See how an extra monthly payment changes payoff time and total interest.

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How to calculate

Each month: interest = balance × monthly rate; principal = payment − interest. Extra principal reduces the next month’s balance.

On a fixed-rate loan, extra principal generally shortens the term and reduces future interest.

Assumes the lender applies the extra amount directly to principal every month with no fee. Confirm prepayment rules with the lender.

Results display up to 8 decimal places; exported numbers preserve calculation precision. This is a calculation summary, not an official certificate.