Methodology & Sources

How the calculators work

Mortgage repayment, extra repayment and offset figures use standard principal-and- interest amortisation formulas, calculated per repayment period (weekly, fortnightly or monthly). Borrowing power estimates apply an illustrative repayment budget with a 3 percentage point assessment buffer. APRA APS 220 requires at least this buffer for authorised deposit-taking institutions; Calcy does not reproduce a lender's full credit assessment. Stamp duty is calculated from each state or territory's own published transfer-duty and first-home-buyer concession rules. Calcy uses illustrative premium bands, a model allowance of 10% and rounding to the nearest $100. These are not insurer quotes or verified state insurance-duty rates. Actual premiums, charges, capitalisation limits and waivers depend on the lender and insurer. First-home-buyer status alone does not remove the model premium.

Where the figures come from

• Interest rates: the Reserve Bank of Australia's published cash rate (rba.gov.au), used as a reference point alongside an editable illustrative mortgage rate, not a verified market average.
• Borrowing power: APRA APS 220 and clearly stated Calcy scenario assumptions.
• Stamp duty and first-home-buyer concessions: each state and territory revenue office's published rates and thresholds (for example Revenue NSW, State Revenue Office Victoria, Queensland Revenue Office).
• HECS/HELP: the Australian Taxation Office's published repayment thresholds.

Individual calculator and guide pages link directly to the specific source used for that page's figures.

Review and editorial process

Calculator and guide pages show a "last reviewed" date. Rates and thresholds change — most often at each state budget, and whenever the RBA moves the cash rate — so figures are checked against the sources above and updated when they change. If you notice a figure that looks out of date, please let us know.

Calcy is operated by Bikash Yadav. Content is reviewed and maintained by the Calcy team for source consistency and calculator accuracy. This review does not imply professional financial certification. AI assistance may be used in drafting or development; financial claims still require verification against official sources. Automated news publication is paused while historical content and publication controls are reviewed.

If you spot an outdated figure or calculation issue, use our Contact channel and include the page URL and official source you believe should be reviewed.

Limitations

Every figure on Calcy is an estimate for general information only, not financial, credit or tax advice. Actual lender rates, fees, eligibility criteria and government charges vary and change. Always confirm exact figures with a licensed Australian mortgage broker, lender, revenue office or financial adviser before making a decision — see our terms of use.