What this loan calculator does
Enter a loan amount and an interest rate, then choose where the payment comes from: the term or the initial repayment rate. The calculator returns the monthly payment, total interest, the remaining debt at the end of the fixed-rate period and an amortization schedule per year or per month – as a table and as a CSV download. Balloon loans, interest-only loans, down payments and extra repayments are covered too. Everything runs locally in your browser.
Payment from the term or from the repayment rate – what is the difference?
There are two ways to a monthly payment. In term mode you decide when the loan should be paid off, and the calculator derives the payment from the annuity formula. In repayment-rate mode you calculate the way German banks quote mortgages: interest rate plus initial repayment rate, for example “3.5% interest, 2% repayment”. The yearly payment is then loan × (interest + repayment) ÷ 100, one twelfth of that per month – and the term is the result, not the input.
The rate is called “initial” because only the first payment matches that ratio exactly: the payment stays constant, the interest share falls as the balance shrinks, so the repayment share grows every month. Be careful with very small repayment rates: if the payment barely covers the interest, the loan practically never ends – the calculator tells you so explicitly instead of pretending a full payoff. In term mode it shows the derived initial repayment rate in return, so you can compare any bank offer directly.
How an annuity loan works
Most consumer and home loans are annuity loans: you pay the same amount every month for the whole term. That fixed payment splits into two parts – interest on the remaining debt, and repayment of the principal. At the start the balance is high, so most of the payment is interest. As the balance shrinks, the interest portion falls and the repayment portion grows. By the final month the loan reaches zero.
What do the fixed-rate period and remaining debt show?
Mortgages usually fix the interest rate only for a fixed-rate period of, say, 10 or 15 years. If you enter it, the calculator reports the remaining debt at that point – the amount you will need to refinance afterwards. It does not change the calculation itself: the schedule keeps running at the entered rate, because nobody knows tomorrow's follow-up rate today.
Down payment, balloon and interest-only loans
The down payment is subtracted from the purchase price – only the rest is financed. The larger the down payment, the smaller the financed amount, the monthly payment and the total interest.
The loan type covers three common models:
- Annuity loan – a constant payment, fully repaid by the end of the term.
- Balloon loan – common in car financing. A large final payment (the balloon or residual value) is only due at the end. This keeps the monthly payment low, but you pay more interest overall because the principal is repaid more slowly. You enter the final payment; the calculator works out the matching monthly rate.
- Interest-only loan – the extreme case: you pay only interest each month and the entire loan amount falls due in one go at the end of the term.
What does an extra repayment do?
A yearly extra repayment is money you put toward the principal on top of the regular instalments. Because it reduces the balance directly, every future interest charge is calculated on a smaller debt. The result is twofold: the loan is paid off sooner, and you pay less total interest – often surprisingly much over a long mortgage.
Repaying early is less exotic than many think, at least in Germany: for general consumer loans – car loans, for instance – Section 502 of the German Civil Code (BGB) caps the early-repayment compensation at 1% of the amount repaid early (0.5% if less than twelve months of the contract remain). That cap does not apply to mortgage loans; there, contracts usually agree a free yearly extra-repayment allowance instead – how much, the contract says.
How do I read and export the amortization schedule?
The schedule shows every period with its interest share, principal repayment, extra repayment and remaining balance – either per year for the overview or per month to verify individual instalments. Download CSV gives you the same table as a file that Excel or LibreOffice opens directly. The numbers use your local format without thousands separators, so the spreadsheet reads them as numbers and sum formulas keep working.
What the calculator does not include
To keep the result clear, this calculator models the core loan mathematics only. Real offers usually add:
- Fees – arrangement, valuation or account fees.
- Rate changes after the fixed period – the calculator reports the remaining debt, but keeps calculating at the entered rate afterwards.
- Commitment interest and staged payouts – for example when a construction loan is drawn in stages.
So treat the numbers as a solid orientation, not a binding quote.
Tips for comparing loans
- Compare the total cost, not just the monthly payment – a longer term lowers the monthly figure but raises total interest.
- A small difference in the interest rate has a large effect over many years.
- Even a modest yearly extra repayment can shorten a long loan considerably.
- With fixed-rate offers, watch the remaining debt: a low payment with a small repayment rate only shifts the problem into the refinancing.
This tool is for information only and is not financial advice. Always confirm the exact figures with your bank or lender before making a decision.