How this model works
Indicative budget-pressure colours: these are custom visual bands based on mortgage repayments as a share of net income: below 30%, 30% to below 40%, 40% to below 50%, and 50% or more. They are not an official mortgage-stress assessment. Expenses, other debt, household size and savings affect affordability. The Australian 30:40 housing-stress indicator instead focuses on lower-income households and housing costs above 30% of gross income. AHURI: understanding the 30:40 indicator.
The timeline uses month-start dates and every RBA rate-effective date, rather than decision announcement dates. A purchase month selects its first day. Selecting a purchase date does not recreate repayments actually paid: this comparison holds the entered balance and remaining term constant. Data coverage starts 1 November 2021. Share results contains only dates, percentage changes and modelling assumptions, excluding salary, balance and dollar repayments.
The spread is the bank-rate input minus the fixed 4.85% RBA anchor (4 November 2026). The default is 7.74% − 4.85% = 2.89 percentage points. This spread stays constant across dates. Changing the bank-rate input recalibrates the spread.
Each date uses the same mortgage balance and remaining term, with monthly principal-and-interest repayments. This isolates the effect of interest rates: it does not amortize your balance between dates or reconstruct your actual loan. Rate changes are passed through immediately and in full. Real lenders use different spreads, timing, fees and repayment conventions. The 7.74% rate is your supplied example, not a verified current ANZ offer.
Income assumptions & formulas
Cash salary = remuneration package ÷ 1.12. Employer super = package − cash salary. Super is excluded from spendable income. Assumes the entire salary attracts 12% super, with no contribution cap or other package benefits.
2026–27 resident tax bands: $0–18,200 at 0%; $18,200–45,000 at 15%; $45,000–135,000 at 30%; $135,000–190,000 at 37%; above $190,000 at 45%. Net income = cash salary − bracket income tax − 2% of cash salary for Medicare. No tax offsets (including LITO), deductions, Medicare low-income reductions/exemptions, Medicare levy surcharge, HELP repayments or other adjustments are included. Low-income results can understate take-home pay. The same tax year is applied at A and Current.
Monthly repayment = P × r ÷ [1 − (1 + r)−n], with r = annual bank rate ÷ 1200 and n = term × 12. At zero interest it is P ÷ n. Negative modeled rates are shown as unsupported. Mortgage burden = repayment ÷ net monthly income. Remaining income excludes all other living expenses; this is not a lender serviceability assessment or personal financial advice.
Verified sources & coverage
RBA history rechecked on 4 November 2026; tax schedule verified during the original build: RBA cash-rate history; RBA 4.85% target effective 4 November 2026; 2026–27 legislated resident tax rates. The last included change was announced 3 November and is effective 4 November 2026. No later November decisions are assumed. Hold decisions are omitted because they did not change the rate.
All data and calculations are embedded. Only opening these source links requires internet. No information is sent anywhere. Calculator inputs last for this open session; reloading restores defaults. Your theme preference is saved in this browser when local storage is available.