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Installment and interest calculator

FinanceThe tool runs here, in your browser.

See what you really pay when you finance a purchase. Enter the amount, the number of installments and the rate, pick the French or German amortization system, and get the installment, the total to pay, the total interest and the financial cost as a percentage. Open the month-by-month amortization table, download it as CSV, or compare installments against paying in cash when there is inflation.

Installment calculator

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What it does

  • Installment and total cost

    The monthly payment, the total you pay back, the interest and the financial cost in one view.

  • Nominal or effective rate

    Enter the rate the way it was quoted to you, nominal annual or effective annual, and the calculator converts it.

  • French or German system

    Fixed payments or decreasing ones: see how each system changes the installments and the interest.

  • Installments or cash?

    With monthly inflation, each payment is brought to today's value to tell you whether financing beats paying up front.

How to use it

  1. 01

    Enter the purchase

    Amount, number of installments and the rate, nominal or effective.

  2. 02

    Read the result

    Installment, total paid, interest and financial cost update as you type.

  3. 03

    Compare or share

    Open the amortization table, download the CSV or copy a link with your numbers in it.

FAQ

Questions people ask

Something else on your mind? Talk to us.

What is the difference between a nominal and an effective rate?

The nominal annual rate is quoted without compounding; the effective annual rate includes it, so it is always equal or higher and shows how much a debt really grows in a year.

What is the difference between the French and German systems?

In the French system every installment is the same amount; in the German system the capital part is fixed, so the installments start higher and decrease.

How do I know whether installments are worth it?

Use the comparison with the cash price and the monthly inflation: if the installments brought to today's value add up to less than the cash price, financing wins.

Is my data stored?

No. The calculation runs in your browser; the share link simply carries your numbers in its address.

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