Savings account: How we calculate
Formulas, rounding and assumptions for this calculation.
How we calculate
Interest accrues on the balance for each calendar day and is added to the account at month-end. The first period runs from the selected date to month-end. The rate stays constant; withdrawals and top-ups are not modelled.
The annual rate is constant, with no deposits or withdrawals. The balance grows with monthly credited interest. Both start and end dates count; the first partial calendar month counts as the first period. Interest rounds to cents when credited monthly. Results are before taxes and fees; choose the 360/365 basis from the bank terms.
Worked example
Start with €1,000 at 3.65% annually, basis 365, on 01.01.2026 for one calendar month. January has 31 counted days: interest = 1,000 × 3.65 / 100 × 31 / 365 = €3.10. The balance on 31.01.2026 is €1,003.10 before tax. The next month earns interest on that increased balance.