What an amortization schedule is
An amortization schedule is a payment-by-payment breakdown of how a loan is repaid, from the very first month to the last. Each row tells you how much of your payment goes to interest, how much actually shrinks the debt (the principal), and the balance still owed. It is the full x-ray of a loan, and it is exactly what banks and credit unions produce for mortgages, personal loans and car finance.
This tool builds the schedule with the French amortization system (fixed installment): you pay the same amount every month, but early on almost all of it is interest, and the principal portion grows month after month. Everything runs in your browser; your figures never leave your device.
How to use it
- Enter the loan amount.
- Type the annual interest rate as a percentage.
- Set the term in months or years.
- Pick a currency to format the figures.
You will instantly see the monthly payment, the total paid, the total interest and the month-by-month table. The toggle switches between a condensed view (first and last months) and the full schedule.
The formula
The fixed payment of the French system comes from the annuity formula:
M = P · r / (1 − (1 + r)^-n)
where P is the amount borrowed, n is the number of installments and r is the monthly rate, that is annual_rate / 12 / 100. Then, for every month:
- Interest for the month =
balance · r - Principal paid =
M − interest - New balance =
balance − principal paid
If the rate is 0%, there is no interest and the payment is simply P / n.
| Item | Symbol | Example |
|---|---|---|
| Amount borrowed | P | 100,000 |
| Monthly rate | r | 0.01 (12% ÷ 12) |
| Number of installments | n | 24 |
| Fixed payment | M | 4,707.35 |
Worked example
A loan of 100,000 at 12% annual over 24 months. The monthly rate is 12 / 12 / 100 = 0.01.
M = 100,000 · 0.01 / (1 − 1.01^-24) = 4,707.35
The monthly payment is 4,707.35. Across 24 payments you hand over 112,976.33 in total, of which 12,976.33 is interest. The balance closes at exactly 0 in the final month.
| Month | Payment | Interest | Principal | Balance |
|---|---|---|---|---|
| 1 | 4,707.35 | 1,000.00 | 3,707.35 | 96,292.65 |
| 2 | 4,707.35 | 962.93 | 3,744.42 | 92,548.23 |
| 12 | 4,707.35 | 571.18 | 4,136.17 | 52,981.56 |
| 23 | 4,707.35 | 92.75 | 4,614.59 | 4,660.74 |
| 24 | 4,707.35 | 46.61 | 4,660.74 | 0.00 |
Notice how in month 1 you pay 1,000 in interest and only 3,707.35 toward principal, while by month 24 nearly all of it is principal. That is the essence of the French system.
Frequently asked questions
Why is my early payment almost all interest?
Because interest is charged on the outstanding balance, and at the start that balance is at its highest. As the debt drops, monthly interest falls and a larger slice of your fixed payment attacks the principal.
Does it work for mortgages and car loans?
Yes. Any fixed-payment loan on the French system amortizes the same way; only the amount, rate and term change. For mortgages, set the term in years and the tool converts it to months.
Will the bank quote the exact same payment?
It will be very close. Lenders often add credit-life insurance, servicing fees or rounding, and some use different day-count bases. Treat this result as a faithful estimate for comparing offers.
What happens if I overpay principal?
An extra lump sum lowers the balance and, with it, all future interest. This schedule assumes regular payments with no overpayments; if you make one, recalculate with the new balance and the remaining term.
How do I handle a 0% rate?
Enter 0 for the rate. The tool splits the amount evenly: the payment is P / n and total interest is zero.