Computed by the rules that loan contracts are written in

Two loan types, as they appear in real contracts

Annuity loans with a constant instalment, where the interest and principal portions shift month by month. They can be defined three ways: by term, by instalment, or by initial repayment rate.

Constant-principal loans, where the principal portion stays fixed and the instalment falls with the remaining balance. That is how private family loans are usually built — not an edge case, but the second calculation path from the start.

What the bank debits, not what an average produces

A mortgage is rarely one loan. A house bank, KfW, a development bank and often a private loan sit side by side — each with its own rate, its own fixed-interest period and its own repayment, in practice sometimes five sources at once.

Homekompass computes each component and then the plan as a whole. A loan's first period is almost never a full month, and that is where approximations break: treat the first month like any other and you are off from the first instalment onwards, and permanently after that.

You see the finished schedule month by month — instalment, the split into interest and principal, the remaining balance, and an opening period marked explicitly as a partial period with its day count.

Commitment interest

Once the bank commits the money it sets it aside — and charges for that until you draw it. Commitment interest appears on no comparison portal and surprises almost everyone on their first bank statement.

Homekompass computes it per period: for each period the undrawn amount, the number of days and the interest due on them. What is reported is the period, never a debit date — because when the bank actually debits is the bank's decision.

Rules, not assumptions

The interest method is not guessed. Calculation follows the German interest method, counting every month as thirty days and every year as three hundred sixty. The house-bank contract and the KfW terms name it verbatim.

Rounding differences land in the final instalment. Across hundreds of instalments, cents accumulate. So that the balance reaches exactly zero, the last instalment differs — in real schedules by a few cents to a few euros. That is exactly what the bank does.

Nominal and effective rates stay separate. They do not follow from one another: the effective rate contains costs the nominal rate does not, such as registering the land charge. Homekompass takes both as the contract states them and derives neither from the other.

Comparing without guessing

Two offers can only be compared honestly as far as both are documented. If one fixed-interest period ends after five years and the other after ten, everything beyond that is an assumption — not a calculation.

Homekompass therefore does not project beyond the agreed fixed-interest period by default. Looking further means choosing an assumption explicitly and seeing it labelled as one. If an offer is missing a figure the comparison needs, the app names the gap instead of filling it — and likewise the schedule stays empty while contract details are missing, rather than inventing dates to produce a plan that does not exist.

What is not included today

Two things are left out: special repayments can be recorded but do not enter the payment series. And payment dates falling on a weekend are not shifted to the next banking day the way banks do. Both are stated here so you do not rely on them.

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