An educational illustration of how mortgage repayments work — how much you'd pay each period and how much interest you'd pay in total over the life of a loan. Change the assumptions, see what moves. Not financial advice.
A standard principal-and-interest mortgage works on an amortisation schedule: each repayment covers the interest that has accrued since the last payment, and whatever is left reduces the outstanding principal. Early in the loan, most of each repayment is interest. As the balance falls, a larger proportion goes to principal.
The chart shows this progression: the blue area is the remaining principal over time and the amber area is cumulative interest paid. The total of both equals total repaid at any given point.
Paying fortnightly instead of monthly (26 payments vs 12) means you are effectively making the equivalent of 13 monthly payments per year rather than 12. The extra payment goes to principal, which reduces the balance on which future interest accrues. Over a 30-year loan this can shorten the effective loan life and reduce total interest significantly. The calculator models this accurately — switch the frequency to see the difference.
Real mortgages involve variable interest rates, fees, redraw facilities, offset accounts, lenders mortgage insurance, and break costs. This calculator assumes a constant interest rate and a clean principal-and-interest structure for the full term. It is an illustration of the mechanics, not a prediction of any actual loan's behaviour.
We'll let you know when it's ready. No noise in the meantime.