How GetRateo calculates
Every number on this site comes from the formulas below. They are published so you can check them against your contract, a spreadsheet, or your lender's own figures. Where a convention is genuinely ambiguous, this page says so rather than hiding the choice.
The instalment
For a loan with equal instalments, the payment that exactly amortizes a balance P over n periods at periodic rate i is P x i / (1 - (1+i)^-n). The periodic rate is the annual nominal rate divided by twelve, which is what almost every EU retail mortgage uses. At a zero rate the formula divides by zero, so the payment is simply P / n. For equal-principal loans the principal slice is fixed at P / n and the interest falls each month, so the instalment starts higher and declines.
Rounding, and why the schedule closes at zero
Every amount is held as a whole number of cents, never as a decimal fraction. Interest is the only float in the calculation and it is rounded, half away from zero, to a whole cent immediately. This matters over 360 rows: with decimal arithmetic the rounding error compounds and the final balance lands a few cents off zero. Here the identity opening balance minus principal minus extra payment equals closing balance holds exactly on every row, the principal column sums to your loan amount to the cent, and the final instalment is adjusted to settle whatever remains. That last adjustment is what real contracts do, and it is why your last payment may differ slightly from all the others.
The APRC
The APRC is not the nominal rate multiplied by twelve. It is the effective annual rate X that solves the equation in Annex I of Directive 2014/17/EU, balancing what you draw down against everything you pay back, fees included, with all intervals expressed in years. There is no closed-form solution, so it is found numerically by bisection over a bracket wide enough to contain any consumer rate. This is the same definition your lender is legally required to publish, which is why the APRC, and not the nominal rate, is the number to compare offers on.
Extra payments
An extra payment is applied after the scheduled instalment in the same month, which is what most EU contracts specify. It then does one of two things, and this is the choice your bank rarely presents clearly. Shortening the term keeps the instalment where it is and ends the loan sooner, which saves the most interest because the balance falls faster for the whole remaining life of the loan. Lowering the instalment keeps the end date and recomputes the payment over the periods that remain, which frees up cash now but saves considerably less overall. The calculator shows both because the right answer depends on whether you need the money back monthly or want the loan gone.
What this does not know
This is a simulation, not an offer, and three things genuinely vary by lender and country. The day-count convention: most monthly annuities divide the annual rate by twelve, but some contracts, Romanian and Spanish ones notably, accrue on actual days over a 360-day year, which changes the numbers on a long loan. Early repayment fees: capped by the Mortgage Credit Directive but transposed differently in each member state, and the default here is zero unless you enter one. And the rate itself: if your rate is variable, the schedule assumes it stays where you set it unless you model a change. Check all three against your contract before acting on any figure here.
How to verify this yourself
Take any scenario and check the instalment against the PMT function in Excel or LibreOffice: PMT(rate/12, months, -amount). It will agree to the cent. The total interest should match the sum of the interest column in the downloadable CSV. If you find a discrepancy against your own contract that is not explained by the three variables above, the difference is worth taking to your lender, because it usually means a fee you were not told about is embedded in the schedule.