Mortgage calculator

A repayment mortgage is amortised: each monthly payment covers the interest accrued that month, and whatever is left reduces the balance. Early on the interest share dominates, which is why the balance barely moves in the first few years and why overpaying early has a disproportionate effect on total cost.

The calculation above assumes a fixed rate for the full term. Most real mortgages are fixed for an initial period and then revert to a variable rate, so treat the total-interest figure as a scenario rather than a forecast — it answers 'what if this rate held' rather than 'what will I pay'.

The figures cover the loan only. Buying a property carries costs that sit outside the mortgage and often surprise first-time buyers: transfer or registration fees, agency commission where the buyer pays, legal fees, mortgage arrangement fees, property insurance, and ongoing service charges on apartments.

Cross-border buyers should also account for currency risk. A loan denominated in one currency against income in another can move the effective cost by double digits over a holding period, and no rate comparison captures that.

The most useful thing an agent can do with a repayment figure is reframe it. A buyer anchored on price often responds better to the monthly difference between two properties than to the gap in headline value, because the monthly number is the one they actually experience.

It also qualifies quickly. A buyer who reacts badly to the realistic monthly figure at current rates is not a buyer at that price, and finding that out in the first conversation saves everyone three viewings.