Methodology and data sources

Everything runs in your browser

Every calculation on CalcAussie is plain JavaScript executed on your own device. The numbers you type are never transmitted to us or to a third party, there is no account to create, and no calculation is stored on a server. That also means results are instant and work on a slow connection.

Formulas are published on the page

Each calculator shows the formula it applies, a worked example, and the assumptions behind the result. If a calculator simplifies something — ignoring intra-year rate changes, for example — that simplification is listed in the assumptions rather than buried.

Rates, thresholds and the financial year

Legislated Australian figures — income tax brackets, the Medicare levy, HELP repayment thresholds, the super guarantee rate, contribution caps, ATO cents-per-kilometre and working-from-home rates — are kept in one central configuration and reused everywhere, so a single update flows through every affected calculator. Each value records the financial year it applies to and the publisher it came from (primarily the ATO, the ABS, Services Australia and state revenue offices).

What we will not invent

Some figures genuinely differ by state, provider or personal circumstance: vehicle registration, land tax, conveyancing fees, electricity tariffs, marketplace commissions, exchange rates, and insurance premiums. For these we give you a clearly labelled, editable input and a prompt to check the current official figure, instead of presenting a made-up national average as if it were authoritative.

Rounding

• Currency is displayed in Australian dollars and rounded for display only — the underlying maths is unrounded.
• Percentages are shown to a sensible number of decimal places for the quantity being measured.
• Dates use Australian conventions (DD/MM/YYYY) and the Australian financial year, 1 July to 30 June.

Testing

Calculation logic is separated from the interface and covered by an automated unit test suite that runs on every change, including catalogue checks that every calculator has a unique URL, unique metadata, a formula, a worked example, FAQs and related links.

Limits

These are estimating tools, not lodgement, advice or compliance software. Read the disclaimer before acting on any figure, and tell us about errors through the contact page.