Common assumptions
Amounts are in nominal Australian dollars. Savings and mortgage calculations use monthly periods. Unless stated otherwise, rates and contributions stay unchanged, savings contributions arrive at the end of each month, and tax, fees, inflation and withdrawals are excluded. Displayed figures are rounded; calculations retain unrounded values.
Compound interest
For a constant annual rate, the monthly rate r is annual percentage ÷ 100 ÷ 12. With initial balance P, monthly contribution C and n months, the future balance is P × (1 + r)n + C × ((1 + r)n − 1) ÷ r. At a zero rate it is P + C × n.
Weekly contributions are multiplied by 52 ÷ 12 and fortnightly contributions by 26 ÷ 12 to obtain monthly equivalents. The result therefore approximates a savings habit rather than reproducing exact daily transactions.
Bank rate models and coverage
Providers come from the public CDR banking-brand register. We request currently offered transaction and savings products, filter some obvious business-only names and retrieve available deposit-rate details. The result can still include specialised, restricted, transaction or offset products. It is not a verified catalogue of all retail savings accounts or all Australian banks. Missing and partial responses are labelled.
The default model uses unambiguous base VARIABLE rates and supported, non-overlapping DOLLAR tiers that cover the balance range. Whole-balance tiers select the applicable rate; per-tier structures weight each portion of the balance. Rates are re-evaluated monthly as the balance changes. A base-rate result does not include BONUS or INTRODUCTORY components. Eligibility, product constraints and fees remain for the visitor to verify.
A custom rate overrides the bank model and stays constant for the whole projection. An explicit conditional scenario is available only for a usable snapshot no more than seven days old, one unambiguous BONUS or INTRODUCTORY adjustment, and supported tiers throughout the plan. Visitors must check the provider conditions and choose that scenario. This assumes eligibility in each modelled period; it does not assess it. Introductory durations must be whole months or years. The full welcome period is assumed to start with the plan, and the model returns to the base rate afterwards. Day-based, stacked, overlapping, incomplete and unsupported structures require manual checking. A retrieved timestamp is not a promise of live data.
Weekly bank data refresh
We schedule retrieval of public CDR product feeds once a week, around Monday morning in Brisbane. This is a snapshot service; rates can change between checks. The overall refresh date describes the latest published run, while each bank has its own retrieval date.
A bank is updated only after all requested product details pass validation. If a request fails, we keep its earlier products and original retrieval date. Large coverage losses stop publication for investigation. Failed, incomplete or more-than-seven-day-old snapshots remain visible for reference but are not automatically applied to calculations. Check the bank’s current offer and enter a confirmed rate when needed. Calculations use code and published inputs; AI does not generate the rates or decide which bank is best for you.
Mortgage and offset
For loan principal P, monthly rate r and n monthly repayments, the standard repayment is P × r ÷ (1 − (1 + r)−n). At zero interest it is P ÷ n. Each month, interest is max(loan balance − constant offset, 0) × r. The regular repayment and extra payment are then subtracted, with the final payment capped to the remaining amount due.
The offset is a separate constant cash balance; it is never automatically spent to close the loan. The standard comparison uses the same principal, rate and term without an offset or extra payments. We do not model interest-only periods, loan fees, partial offsets, rate changes or individual lender rounding.
Home deposit and LVR
Loan = purchase price − deposit towards the price + costs financed in the loan. LVR = loan ÷ lender valuation × 100. A blank valuation uses the purchase price. Additional reduction to reach 80% = max(0, loan − 0.8 × valuation). Thresholds use unrounded values. The visual bar separates the price into deposit and borrowing; it excludes added loan costs. This calculator does not assess affordability, government support, lender approval or LMI premiums and waivers.
Savings goals
The monthly contribution needed is max(0, (target − P × (1 + r)n) × r ÷ ((1 + r)n − 1)). At zero interest it is max(0, (target − P) ÷ n). This does not calculate property purchase costs, transfer duty, grants, mortgage insurance or loan eligibility.
Emergency funds
Target = essential monthly expenses × selected months. Gap = max(target − existing dedicated savings, 0). Months to goal = gap ÷ monthly contribution, rounded up. A positive gap and zero contribution has no estimated completion time. Interest is excluded.
Salary and take-home pay
The take-home pay calculator uses schedules 1 and 8 of the ATO Withholding Schedules Instrument 2026, effective 1 July 2026. It covers Australian tax residents with a TFN and standard Medicare treatment, with optional tax-free-threshold and student-loan settings. Medicare is included in the PAYG amount, not deducted twice.
Weekly equivalents discard cents and add $0.99 before applying the appropriate coefficient. Weekly withholding is rounded first, then multiplied by 2 for fortnightly pay or 13 ÷ 3 for monthly pay, with monthly withholding rounded again. Monthly earnings ending in 33 cents receive the ATO one-cent adjustment before conversion. The annual estimate is based on twelve monthly pays, not a final tax assessment. We compare the formula against the ATO's published sample amounts.
Salary inputs convert using 52 weeks, 26 fortnights or 12 months. The standard employer-super estimate is 12% of qualifying earnings, capped at the 2026–27 annual maximum contribution base of $270,830. For inclusive packages, cash salary and employer super are separated first. A contractual annual employer contribution can override the standard estimate. Salary sacrifice and special payroll circumstances are excluded; the calculator page lists the scope.
Occupation earnings comparison
We compare gross weekly cash pay, excluding employer super, against published percentile cutoffs in ABS Employee Earnings and Hours, May 2025 (released 23 January 2026). Data cube 3, table 10 covers all employees; data cube 8, table 8 covers full-time non-managerial employees paid at adult rates. The comparison uses the Persons rows, not one sex alone. We show the enclosing published percentile band without interpolating an exact rank. Job groups are broad and do not control for hours, location or experience. This is a historical comparison, not a current salary valuation.
Sources and corrections
- CDR product data and provider discovery
- Australian Consumer Data Standards
- Moneysmart compound interest calculator
- Moneysmart mortgage calculator
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