Understand the standard amortising repayment
A principal-and-interest repayment covers interest charged for the period and reduces the amount borrowed. Early in a long loan term, more of each payment commonly goes to interest; as the balance declines, more goes to principal under a constant-rate schedule.
This calculator provides a clean monthly estimate from the loan amount, annual rate and term. Actual mortgage repayments can differ because of daily interest, lender rounding, fees, offset balances, redraw activity, repayment dates and changes to the variable or fixed rate. For a quote or existing account, rely on the lender’s current repayment notice and loan contract.
How to read the results
Principal & interest repayment is the level monthly payment that amortises the entered amount over the selected term at a constant monthly rate. Total interest is the modelled interest across all payments, while Total repaid is principal plus that interest.
Final payment is the exact amount required at the end of the schedule and can differ by cents from the regular payment because the model prevents overpayment. The projected balance chart is a mathematical schedule, not a lender statement or approval assessment.
Worked example
For the default $650,000 loan at 6.34% over 30 years, the estimated principal-and-interest repayment is $4,040.29 per month. The modelled total interest is $804,503 and total repaid is $1,454,503.
The final payment is $4,040.29 after rounding to cents in the displayed result. It assumes the rate and repayment remain unchanged for all 360 monthly payments.
A lender may collect a slightly different amount because its daily-interest and rounding conventions can differ.
Assumptions and limitations
- The loan is fully amortised through 360 monthly payments in the default example.
- The entered annual interest rate remains constant for the entire term.
- Interest is modelled monthly before each repayment.
- No establishment fees, monthly fees, offset funds, redraws or extra repayments are included.
- The calculation does not assess borrowing capacity, loan approval or product eligibility.
Frequently asked questions
What does principal and interest mean?
Each repayment pays accrued interest and also reduces the original amount borrowed.
Why is the interest total so large?
Interest is charged over many months on the outstanding balance; the result is sensitive to the rate and term.
Can I use this for a fixed loan?
It can illustrate the fixed-rate period only if the rate stays constant; future repayments after expiry may differ.
This calculator and supporting information provide general estimates only. They do not take account of every product rule, tax consequence or personal circumstance and are not financial, tax, credit or legal advice.