The bank shows you a payment. This shows you the shape of the loan — and what dragging one slider does to twenty years of interest. Works for any currency.
Every extra unit goes straight at the principal, and all future interest is computed on the smaller balance — that’s why modest extras snowball. The math here keeps your required payment fixed and shortens the term, which is how most lenders apply overpayments by default. (Some instead recalculate a lower payment over the same term — less powerful; ask yours.)
Two honest caveats. Some fixed-rate mortgages cap penalty-free overpayment (commonly ~10% of the balance per year) — check your terms. And if you carry more expensive debt elsewhere, arithmetic says feed that first.
It’s the standard amortization formula — the same one your bank uses — with interest compounded monthly on the remaining balance. Real schedules can differ by a few units from rounding to cents and by start-date conventions; the shape and the savings are what to trust. Currency doesn’t matter to the math: type amounts in whatever you borrow in.
Yes — 12,5 and 12.5 both work, and thousands separators are fine
(1,234.56 or 1.234,56). A lone comma followed by exactly three digits,
like 1,234, is read as one thousand two hundred thirty-four.
Entirely in your browser. Numbers you type are never sent anywhere — there is no server doing the math, no analytics watching you do it.