Amortization Calculator
Generate a full loan amortization schedule showing principal, interest, and balance for every payment, with optional extra payments.
About the Amortization Calculator
An amortization schedule is the detailed, payment-by-payment breakdown of exactly how a loan is repaid: how much of each payment is interest, how much is principal, and what the remaining balance is afterward. This calculator generates that schedule for any fixed loan, and lets you add an extra monthly payment to see how much faster the loan is paid off.
How It Works
Starting from the loan balance, the calculator computes the standard fixed monthly payment for the given rate and term, then walks month by month: each month's interest is the remaining balance times the monthly rate, and the rest of the payment (plus any extra amount you specify) reduces principal. The loan is fully paid once the balance reaches zero, which happens sooner than the original term if extra payments are included.
Interest(month) = Balance × monthly rate; Principal(month) = Payment + Extra − Interest(month); Balance = Balance − Principal(month).
Example
Scenario: A $250,000 loan at 6% for 15 years with a $200 extra monthly payment.
Result: Base payment of about $2,109/month; with the extra $200 applied, the loan pays off several years early and total interest drops noticeably versus the scheduled 15-year payoff.
Assumptions & Limitations
- Extra payments are assumed to apply entirely to principal, which is standard for most mortgages and installment loans.
- Uses a fixed rate for the full amortization period.
- The displayed schedule shows the first 12 rows for readability; the totals reflect the complete schedule.
- Some loans have prepayment penalties — check your loan terms before applying extra payments in real life.