Amortization Schedule Calculator
Generate a full month-by-month amortization schedule for any fixed-rate loan, with optional extra payments.
| Year | Principal paid | Interest paid | Ending balance |
|---|
What an amortization schedule shows
An amortization schedule breaks every single payment on a fixed-rate loan into two pieces: the portion that goes toward interest and the portion that reduces your principal balance. Early in the loan, most of each payment is interest; by the final payments, almost all of it goes to principal. This calculator generates that full schedule for any loan amount, rate, and term, and lets you see the effect of adding a fixed extra payment every month.
The formula
Each month: interest due = remaining balance × (APR ÷ 12). Principal paid = payment − interest due. New balance = old balance − principal paid. The fixed monthly payment itself is P × [r(1+r)n] ÷ [(1+r)n − 1].
Why extra payments have such a big effect
Because interest is calculated on your remaining balance, every extra dollar you put toward principal reduces the interest charged in every future month of the loan — not just that one payment. That's why even a modest extra payment can shave years off a mortgage or auto loan and save thousands of dollars in interest, as you can see by comparing the "total interest" figure with and without an extra payment amount above.
Frequently asked questions
Why does more of my payment go to interest at first?
Interest is charged on your current balance, which is largest at the start of the loan. As the balance shrinks with each payment, less interest accrues and more of your fixed payment is freed up to pay down principal — a pattern often visualized as the 'amortization curve.'
What happens if I add an extra payment?
Extra payments go straight to principal, which shrinks your balance faster than scheduled. That reduces both the interest charged going forward and the total number of payments needed to reach zero, which is exactly what the payoff-time and total-interest figures above reflect.
Can I download this schedule?
Yes — click "Download CSV" to save the full month-by-month schedule as a spreadsheet file you can open in Excel, Google Sheets, or Numbers.
Does this work for any loan type?
Yes, as long as it's a fixed-rate, fully amortizing loan — mortgages, auto loans, personal loans, and student loans with a fixed rate all use the same amortization math.