Most German property loans are not fully repaid when the fixed-interest period (Zinsbindung) ends — a remaining debt (Restschuld) is left that needs to be refinanced. If interest rates are higher then than at signing, the monthly payment can rise significantly. Our calculator determines the remaining debt at the end of the fixed period and shows the payment you can expect for the follow-up financing.
How to use this calculator
The calculator simulates the amortization of your annuity loan over the fixed-interest period:
- Step 1: Enter the original loan amount.
- Step 2: Enter the current interest rate and the initial repayment rate — together they make up your annuity.
- Step 3: Choose the length of the fixed-interest period (10 or 15 years are common).
- Step 4: Enter the expected follow-up interest rate. The calculator assumes the repayment rate is kept unchanged.
Understanding the results
The calculation shows where you stand at the end of the fixed period:
- Remaining debt: the part of the loan not yet repaid, which needs follow-up financing.
- Amount repaid: how much of the loan you have already paid off during the fixed period — the repayment share grows year by year.
- Current and new monthly payment: today's payment compared with the payment after refinancing at the new rate.
- Difference per month: the additional or reduced monthly burden — the decisive number for your cash flow planning.
Why refinancing belongs in the investment calculation
Anyone calculating with today's low payment easily underestimates the interest rate risk: with a typical financing of 10 years fixed interest and 2% repayment, often more than 70% of the loan is still outstanding at the end of the fixed period. If rates rise by two percentage points during that time, the new payment can flip a rental property's cash flow from positive to negative. Investors should therefore plan the follow-up financing from day one: calculate with conservative rate assumptions, choose a sufficiently high repayment rate and use extra repayment rights (Sondertilgung) to push down the remaining debt. Acting early also lets you lock in the follow-up rate several years in advance with a forward loan.
Tips
- •Ten years after full disbursement you can terminate any loan under §489 BGB with six months' notice free of charge — even with a longer fixed-interest period.
- •A forward loan locks in today's rate for a refinancing in the future — for a small rate premium per month of lead time.
- •Always compare several offers for the follow-up financing: your current bank is rarely the cheapest option, and switching lenders at the end of the fixed period is free.