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Annuity payment calculator

Enter the loan amount, annual interest rate and term in months. The calculator works out the monthly payment, total interest, and shows how the outstanding balance declines.

Result

Monthly payment

Total amount paid
Total interest paid

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This calculation is for informational purposes only and does not replace advice from a qualified professional. Formulas and rates may not fit your exact situation — double-check the figures before making decisions.

How it is calculated

An annuity payment stays the same for the entire loan term, even though the split inside it keeps changing: early on, most of the payment goes to interest; toward the end, almost all of it goes to principal.

Formula: payment = loan amount × monthly rate × (1 + monthly rate) ^ number of months ÷ ((1 + monthly rate) ^ number of months − 1), where monthly rate = annual rate ÷ 12 ÷ 100.

Total interest = total amount paid − loan amount. Over the full term, annuity payments usually cost more in total interest than a declining-payment ("differentiated") schedule, where the principal is repaid in equal chunks and the payment shrinks over time — but in exchange, the annuity payment is predictable and doesn't front-load a heavier burden in the first months the way a declining schedule does.

The balance chart shows it doesn't decline in a straight line but along an accelerating curve: the first payments barely dent the principal, and most of the paydown happens in the second half of the term.

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