What Does Your Mortgage Really Cost?

Numbers in hand. Now find a rate that matches your profile.

The calculator gives you the estimate. LoanGorilla gives you the actual rate a lender will offer — based on your borrower profile, not a generic assumption.

How this Repayment Calculator works

A Home Loan Repayment Calculator estimates what your mortgage repayments may look like based on the loan amount, interest rate, term, repayment frequency and repayment type. In most cases, it is calculating the amount needed to repay the loan over time under the assumptions you enter, while showing how much of that cost is interest versus principal.

PMT = [P × r × (1+r)ⁿ] / [(1+r)ⁿ – 1]

In plain English: P is your loan amount, r is the interest rate per repayment period (annual rate ÷ payments per year), and n is the total number of payments. The result is your scheduled repayment — the fixed amount you'd pay each week, fortnight or month under the chosen assumptions.

That sounds simple, and mostly it is. The useful part is not the formula. It's what the formula forces you to confront: change the rate by a small amount, shorten the term, add extra repayments or switch from interest-only to principal-and-interest, and the shape of the loan changes immediately.

This calculator is a guide, not a guarantee. It:

• Uses the loan amount, rate, term and frequency you enter to estimate repayments over time.
• Assumes the rate stays at the level you model unless you toggle the stress-test buffer.
• Treats the repayment type selected as the structure used for the estimate.
• Models offset and extra repayments when toggled on, but does not include every lender fee, package charge or future rate movement.
• Shows a clean estimate of loan repayment behaviour, not a perfect replica of every product's real-world cashflow.

Offset, redraw and extra repayments — explained

These three ideas get thrown into the same bucket all the time, which is convenient for lazy marketing and terrible for borrower clarity. They're related, but not identical.

Two borrowers can both be "paying extra" and still get very different results depending on whether the money sits in offset, is paid into the loan directly, or is expected to remain accessible later. Use the toggles in the calculator to see exactly how each behaves on your loan.

How to interpret your results

Don't read the repayment result like it's a verdict from the heavens. Read it like a stress test for your lifestyle. A repayment that looks technically possible may still be strategically stupid if it wipes out your buffer, your flexibility or your ability to handle even mild financial turbulence.

The healthiest way to interpret the result is in layers:

• Base repayment. What the loan may cost under the assumptions you entered.
• Tougher repayment. What happens if rates rise, especially on variable loans (toggle the +3% stress test).
• Total cost. What the loan does over decades, not just next month.
• True affordability. Whether the repayment still fits after groceries, insurance, transport, childcare, repairs and all the other charming little costs adulthood keeps adding to the script.

If the repayment only works in the most flattering version of your budget, it doesn't really work. That's not pessimism. That's the calculator doing its job.

How to find a repayment that fits your budget

The job is not to force your life to fit the maximum repayment. The job is to find a repayment range that leaves room for reality. That usually means stepping back from the biggest possible loan and testing a few cleaner scenarios.

• Start with your expected loan amount, or use the Borrowing Power Calculator if you don't know it yet.
• Run the repayment at the current likely rate.
• Run it again at a tougher rate — toggle the +3% stress test for variable scenarios.
• Compare 25-, 30- and 35-year terms to see the trade-off between monthly relief and long-term interest pain.
• Compare weekly, fortnightly and monthly options where relevant.
• Test whether extra repayments are realistic, not fictional.
• Then compare home loans once you know what level of repayment and flexibility your life can actually handle.

The Rebel impulse says "we'll make it work." The Sage impulse says "show me the version that still works after a bad month, a rate jump and a surprise tradie invoice." LoanGorilla is firmly on speaking terms with the second one.

Calculator assumptions

This calculator estimates repayments using the standard amortisation (annuity) formula and assumes the rate you enter holds for the full term unless the stress-test buffer is toggled on. Interest-only periods cover interest only — principal isn't reduced during that phase, and the post-IO repayment is recalculated on the remaining balance and remaining term. Offset modelling assumes a constant offset balance reducing the interest base each period. Extra repayments are applied at every period at the amount you enter. Application fees, annual fees, package charges, break costs, redraw rules, valuation costs and product-specific restrictions are not included. Variable-rate movements aren't predicted; use the stress-test toggle to model a tougher rate scenario manually. The calculator does not constitute financial advice. Reviewed by the LoanGorilla editorial team — last updated May 2026.