Loan calculator
Calculate the monthly payment of a loan, the total to pay, the total interest, and the full amortization schedule (French system).
What this calculator does
This calculator finds the fixed monthly payment of a loan using the French amortization system, the one most banks and lenders use. You enter the amount, the annual rate, and the term (in years or months) and get the payment, the total you will pay, the total interest, and the full amortization schedule.
The schedule shows, month by month, how much of each payment goes to interest and how much reduces your debt, until the balance reaches exactly zero. For terms longer than 5 years, payments are grouped by year to keep the table readable.
Who it is for
- People evaluating a personal, car, or mortgage loan who want to know if the payment fits their budget.
- Anyone comparing offers with different rates or terms who needs to see the total cost of each.
- Borrowers who already have a loan and want to understand how much interest they pay each month.
- Anyone who wants to see the effect of shortening or extending the term before signing.
What information you need
- The loan amount: what you receive from the bank or lender.
- The nominal annual interest rate as a percentage.
- The term in years or months (whole numbers).
How it is calculated
The monthly rate is the annual rate divided by 12 (monthly compounding). With that rate, the French system formula finds the fixed payment that amortizes the whole loan in the exact number of months.
Each month, interest is calculated on the outstanding balance and the rest of the payment reduces the debt. That is why you pay more interest at the start and almost everything goes to principal at the end.
If the rate is 0%, the payment is simply the amount divided by the number of months.
The schedule is computed in integer cents: the payment and each month’s interest are rounded to 2 decimal places (half up), and the final payment is adjusted by the accumulated rounding cents so the final balance is exactly $0.00.
Formula
- Monthly payment (French system)
payment = amount × i ÷ (1 − (1 + i)^−n), with i = annual rate ÷ 12 ÷ 100- Zero-rate payment
payment = amount ÷ n- Monthly breakdown
interest = balance × i · principal = payment − interest · new balance = balance − principal
Worked example
You borrow $10,000 over 24 months at a 12% annual rate. How much will you pay each month and what will the loan cost you?
- Monthly rate: 12% ÷ 12 = 1% (i = 0.01).
- Payment: $10,000 × 0.01 ÷ (1 − (1.01)^−24) = $470.73.
- First month: interest = $10,000 × 0.01 = $100.00; principal = $470.73 − $100.00 = $370.73; balance = $9,629.27.
- The final payment is adjusted to $470.86 so the balance ends exactly at $0.00.
- Total paid: $11,297.65. Total interest: $11,297.65 − $10,000 = $1,297.65.
You will pay $470.73 per month (the final payment is $470.86) and the loan will cost you $1,297.65 in interest.
How to interpret the result
The payment is fixed, but its composition changes: at the start most of it is interest. If you plan to prepay principal, doing it early saves the most interest.
Extending the term lowers the payment but raises the total cost: always compare the total interest, not just the payment.
The result does not include fees, insurance, or other charges the bank may add to the payment; the APR or total credit cost in your contract may be higher.
Common mistakes
- Comparing loans by the monthly payment alone: a lower payment over a longer term almost always means paying more interest in total.
- Confusing the nominal annual rate with the effective rate or the total credit cost (which includes fees and insurance).
- Assuming that halfway through the term you have paid off half the debt: because of early interest, the principal falls more slowly at first.
- Entering the monthly rate in the annual rate field: if you are quoted 1% monthly, enter 12.
Frequently asked questions
What is the French amortization system?
It is the fixed-payment system: you pay the same amount every month and, within the payment, the interest portion shrinks while the principal portion grows. Most personal, car, and mortgage loans use it.
Why is the final payment slightly different?
Because the payment is rounded to the cent each month, and those roundings accumulate a small difference. The calculator adjusts the final payment (in this example, $470.86 instead of $470.73) so the balance closes exactly at zero, just like banks do.
What happens if I prepay principal?
An extra payment reduces the balance, and with it the interest of every following month. Depending on your contract, it can shorten the term or lower the payment. This calculator shows the plan without prepayments; use it as a baseline for comparison.
Is the rate I enter the APR?
Not necessarily. This calculator uses the nominal annual rate with monthly compounding, without fees or insurance. Your bank’s total credit cost includes those charges, which is why it is usually higher than the nominal rate.
Can I calculate an interest-free loan?
Yes. With a 0% rate, the payment is the amount divided by the months: $1,000 over 3 months is two payments of $333.33 and a final one of $333.34 to complete exactly $1,000.
Sources
- Last reviewed:
- July 20, 2026
- Calculation version:
- 1.0.0
Important notice
The results of these calculators are informative estimates and may differ from official calculations. They do not constitute legal, tax, or financial advice. Always verify with the competent institutions or a professional.
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