Is there a calculator for 10/15/20-year comparisons?
Yes — the fixed-period fields below accept any term from 1 to 40 years, so 10 vs. 15, 10 vs. 20 or 15 vs. 20 can all be compared.
Calculator · Fixed-rate period
Break-Even Rate Calculator
10 or 15 years fixed — which pays off? The calculator shows the follow-up rate the shorter fixation can reach at most before the longer one becomes the better deal. Mortgage interest rates in Germany move independently of a borrower's country of residence.
At what follow-up rate does the longer fixed-rate period pay off?
The break-even rate is the highest follow-up interest rate a shorter fixed-rate period can reach without becoming more expensive overall than a longer fixed-rate period taken from the start. It's calculated by projecting the shorter option's remaining balance at the end of its fixed period forward at a rate that makes it meet the longer option's remaining balance at the same point in time. If the actual follow-up rate ends up below that figure, the shorter fixation was cheaper; above it, the longer fixation would have paid off. The comparison matters most when the premium for the longer fixation is small — then the break-even rate often sits well above today's market level, meaning the extra security costs very little in practice. The calculator below computes the break-even rate for your two offers. Not legal or tax advice.
Short answer
Comparing fixed-rate periods, in three points
What does it calculate?
The break-even follow-up rate: the highest rate the shorter fixation could face without becoming more expensive over the comparison period than the longer one.
Is the longer period always better?
Safer, not automatically cheaper — it usually costs a small rate premium (often 0.2–0.5 percentage points) in exchange for planning security.
Break-Even Rate Calculator
Your comparison
One loan, two offers with different fixed-rate periods. Initial repayment rate is the same for both; the payment stays constant when moving into follow-up financing.
Result (indicative)
Break-even follow-up rate
Monthly payment (same for both)
Balance A after period A
Balance B after period B
Non-binding model calculation, following the methodology of Stiftung Warentest's Zinsbindungsrechner: both variants use the same monthly payment (derived from offer B at the stated initial repayment rate); the interest saved by the shorter fixation flows into faster principal repayment. The same payment is assumed to continue into follow-up financing. The actual follow-up rate years from now is not known today.
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Repayment
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Payment, remaining balance and schedule for a single offer.
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Early repayment penalty
A rough estimate of what an early payoff costs.
Early repayment penalty →Follow-up
Follow-up financing
What happens to the remaining balance after the fixed-rate period.
Follow-up financing →Why compare at all
Two offers, one comparable number
A lower rate alone doesn't say much if the fixed period is shorter — the shorter fixation carries a follow-up risk whose price is unknown today. The break-even rate makes the two offers comparable: it names the exact point at which betting on a cheap follow-up rate stops paying off.
In practice the comparison matters most when the premium for the longer fixation is small — often just 0.2 to 0.5 percentage points. Then the break-even rate often sits well above what's realistic in the market, and the extra security of the longer fixation costs very little in real terms.
What the calculator can't do
A model, not a forecast
- The future rate is unknown. The break-even rate is a comparison figure, not a prediction. It doesn't tell you what the rate will actually be in ten years — only the level above which the shorter fixation turns out to have been more expensive in hindsight.
- Personal flexibility matters too. If you plan to sell, refinance, or make extra repayments in the coming years, weigh that more heavily than the pure interest math — shorter fixations are often more flexible in their terms.
- Creditworthiness can change. A long fixation locks in not just the rate but also financeability — relevant for foreseeable changes such as self-employment, retirement, or moving abroad.
We put the break-even rate into the context of your actual situation — including which bank offers both terms at all for your constellation.
FAQ
Frequently asked questions
What is the break-even rate on a German mortgage?
The highest follow-up interest rate a shorter fixed-rate period can reach without becoming more expensive over the whole comparison period than a longer fixed-rate period taken from the start. It's calculated from the remaining balance of both offers at the end of their respective fixed periods.
Is the longer fixed-rate period always the safer choice?
Safer, yes — cheaper, not automatically. It usually costs a rate premium over the shorter fixation. Whether that pays off depends on the break-even rate — and on how much you value planning security over pure interest savings.
Why is the break-even rate often higher than today's market rate?
Because the premium for the longer fixation is usually small (often 0.2 to 0.5 percentage points), while it compounds against the shorter fixation's rate advantage over many years. The smaller the premium and the bigger the gap in fixed periods, the higher the break-even rate sits above today's rate level.
Does the payment really stay the same in follow-up financing?
That's a modelling assumption of the calculator, not a rule. In practice, the payment in follow-up financing is usually renegotiated or deliberately adjusted. The assumption still allows a fair comparison because it's applied equally to both offers.
What if the calculator shows "no intersection"?
This means the shorter fixation doesn't meet the longer fixation's remaining balance even at a very low or very high follow-up rate — usually because the input values are far apart. Double-check the fixed period and interest rate for both offers.
Is there a German mortgage calculator to compare fixed-rate periods (10/15/20 years)?
Yes — this break-even rate calculator. The fixed-period fields accept any term from 1 to 40 years, so you can compare 10 vs. 15, 10 vs. 20, 15 vs. 20 or any other pairing; the defaults shown are 10 and 15 years. It calculates the follow-up rate at which the shorter fixation becomes more expensive than the longer one.
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