Repayment Calculator 2026: work out your monthly instalment, remaining debt and repayment plan

Understanding repayment: the fastest route to being debt-free

With the annuity loan (Annuitätendarlehen) — the usual form of construction financing in Germany — you pay a constant instalment over the entire fixed-interest period. This instalment is made up of two parts: the interest and the repayment. Initially the interest portion is high and the repayment portion small. With every payment the remaining debt falls, which reduces the interest portion and the repayment portion rises by itself. This acceleration effect forms the core of every repayment: the higher you set the initial repayment, the faster it takes effect.

Change the initial repayment in the calculator and watch the total term: with only 1 percent repayment, loans in 2026 stretch well beyond 40 years — at 3 percent you are often debt-free after a good 25 years. The second big lever is the special repayment. Because it immediately reduces the remaining debt, every euro paid in saves interest over the entire remaining term. Most banks grant a free special repayment right of 5 to 10 percent per year — when signing, make sure no interest surcharge arises.

The remaining debt as the central figure

The low monthly instalment tells only half the story. What matters is what remaining debt is left at the end of the fixed-interest period, because it is exactly this sum that you carry forward via a follow-up financing at the interest rate applicable then. A high remaining debt means an interest-rate-change risk. Anyone who wants to limit it opts for a higher repayment, a longer fixed-interest period or firmly plans in special repayments. How the interest level for housing loans develops is documented by the interest statistics of the Deutsche Bundesbank; independent tips on construction financing are provided by the Consumer Advice Centre (Verbraucherzentrale). How to combine all of this with equity and total costs is shown to you by the mortgage calculator, and you will find the currently valid interest rates under current construction interest rates. The detailed roadmap is provided by the guide Construction financing 2026.

For prefab house builders, a further building block comes into play: the low-interest KfW subsidised loans. They can be integrated into almost any financing and reduce the average interest burden. Which programmes come into question for your project can be read in the guide on the KfW loan for buying a house. The binding terms are published by the KfW development bank.