Loan Interest Calculator

Calculate loan interest

Find out how much a loan will cost you in interest and what share of the principal that represents. Useful for comparing the real cost of different offers or terms: you need the amount, interest rate and duration in years.

Calculate your loan interest

Result

Total interest

€3,199.35

Monthly payment: €386.66
Total repaid: €23,199.35
Interest relative to principal: 16%

Formula version: 1.0.0

Show year-by-year breakdown

Year	Paid	Interest	Principal repaid	Balance
1	€4,639.92	€1,103.81	€3,536.11	€16,463.89
2	€4,639.92	€885.72	€3,754.20	€12,709.69
3	€4,639.92	€654.16	€3,985.76	€8,723.93
4	€4,639.92	€408.33	€4,231.59	€4,492.34
5	€4,639.67	€147.33	€4,492.34	€0.00

How to use the loan interest calculator

Enter the loan amount.
Enter the annual interest rate and the duration in years.
Review the total interest, the payment and interest as a share of the principal.

How loan interest is calculated

Interest = payment × number of payments − principal

Each month you pay interest on the outstanding balance. It's highest at the start and falls as the loan is repaid.

Loan interest example

A €20,000 loan at 6% over 5 years has a €386.66 payment and costs €3,199.35 in interest: 16% of the principal.

Illustrative example with the data shown; not a guaranteed outcome.

Assumptions and limitations

Fixed-rate loan with a constant monthly payment.
Fees and insurance are not included.

Frequently asked questions

How can I pay less interest?

With a lower rate, a shorter term or by repaying early.

Is the interest the same every month?

No: it's calculated on the outstanding balance, so it falls over time.

Related calculators

See loans & mortgages calculators

Indicative result for information only; not financial or tax advice. Read the legal notice · How we calculate results

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