Calculators

How is loan interest calculated? Formula and example

Learn the annuity formula, monthly rate and principal-interest split with a practical 10,000 AZN example.

A monthly loan payment is not found by simply dividing the amount by the number of months. Interest is charged on the outstanding principal and the repayment method determines how each payment is split.

What is an annuity payment?

With an annuity schedule the monthly payment normally remains level. Early payments contain more interest; as the balance falls, a larger share goes to principal.

The monthly payment formula

A = P × r × (1+r)n / ((1+r)n − 1), where P is principal, r is the monthly rate, n is the number of months and A is the payment. A 12% nominal annual rate corresponds to 1% per month, represented as 0.01 in the formula.

10,000 AZN for 36 months

At a 12% nominal rate, the monthly payment is approximately 332.14 AZN. Total scheduled repayments are about 11,957.15 AZN and interest is 1,957.15 AZN before fees and insurance. Use the loan calculator to change the assumptions and see the full chart.

How the term changes the result

A longer term spreads principal across more months and lowers the payment, but interest is charged for longer. A shorter term increases the monthly burden while often reducing lifetime interest.

Common calculation mistakes

  • using the annual rate as a monthly rate;
  • entering years where the formula expects months;
  • ignoring fees and insurance;
  • choosing a long term based only on the monthly figure.

See the calculation methodology for assumptions and rounding.

Check your numbers

Calculate the payment and total cost in the loan calculator, then compare different terms side by side. Loan calculator · Compare plans.

Editorial note

This article is informational and is not individual financial advice. Assumptions are documented in the methodology and content standards in the editorial policy. Calculation methodology · Editorial policy.

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