Close
Loan Amortization Schedule Calculator
Produces a period-by-period amortization schedule for a fixed-rate loan: level payment split into interest and principal, with the closing balance carried forward.
How this calculation works
- The level payment is the annuity payment that retires the principal over the term at the periodic rate. The periodic rate is the annual rate divided by the number of payments per year.
- Each period, interest is the opening balance multiplied by the periodic rate. Principal is the payment less that interest, and the closing balance is the opening balance less the principal.
- Because interest is charged on a declining balance, the principal share of a level payment rises over the term while the interest share falls.
- Extra payments are applied to principal, which shortens the term rather than reducing the scheduled payment.
Conventions and edge cases
- The final payment is almost never exactly equal to the others. Rounding each period to cents leaves a small stub, which the schedule trues up in the last payment so the closing balance lands exactly at zero.
- A zero interest rate is handled as a straight division of principal across the term rather than as a division by zero.
- This assumes a fixed rate and a level payment. Variable-rate, interest-only, and balloon structures are not modelled.
Frequently asked questions
- Why is the last payment different from the others?
- Rounding. Each period's interest and principal are rounded to cents, and those roundings accumulate over the term. The final payment absorbs the difference so the loan closes at exactly zero rather than a few cents either side. Lenders do the same thing.
- How do extra payments change the schedule?
- Extra principal reduces the balance that interest is charged on for every subsequent period, so the loan retires early. The scheduled payment stays the same; the term shortens and total interest falls.
- Does this handle interest-only or balloon loans?
- No. It models a fixed-rate loan with a level payment that fully amortizes over the term. Interest-only periods, balloon payments, and variable rates each change the payment calculation and are not covered.