Monthly mortgage payment and total interest
Monthly payment, interest paid and the total cost of the loan.
How the payment is calculated
The calculator uses an annuity — the same payment every month. The formula: the loan amount is multiplied by the monthly rate and divided by one minus (1 + rate) to the power of “minus the number of months”. Inside the payment the share of interest gradually falls and the share of principal grows, but the total does not change — so the budget can be planned years ahead.
What the overpayment shows
Overpayment is the difference between all payments and the loan amount. It depends on the rate and the term: interest is charged on the outstanding debt, and the longer you pay, the longer interest accrues on the balance. Three million at 12% over 20 years is an overpayment of more than four million, while the same three million over 10 years is noticeably cheaper, although the payment is higher.
What is missing from the calculation
Insurance, origination fees, property valuation, state duty and a possible rate change are not included. Early repayments are not accounted for either — with them the overpayment would be smaller and the term shorter. So the figure from the calculator is the base cost of the loan, not the full cost of the deal: check the final terms in the payment schedule from the bank.
When comparing bank offers, look not only at the rate but also at the total cost of credit and the terms for early repayment without fees.
Frequently asked questions
Which payment is calculated?
An annuity payment, the same every month. It is the scheme mortgages are most often sold on, because the payment is predictable for a household budget.
Are early repayments taken into account?
No, the calculation assumes none. Overpaying reduces the interest and shortens the term; the calculator shows the baseline scenario.
Why does the interest depend so much on the term?
Interest is charged on the outstanding balance. The longer you pay, the longer interest accrues on that balance, so 30 years costs noticeably more than 15.
Related tools
Checked: 26 October 2026. For reference only — the result depends on the material and the skill of the installer.