calx.io/Methodology

calx is a set of Australian financial calculators built on one principle: trust through accuracy. Every rate comes from published Australian Taxation Office (ATO) or state revenue office material, every calculation runs in your browser, and every calculator links to its sources. There are no ads, no accounts and no tracking of your figures.

• ATO: income tax brackets, Low Income Tax Offset, Seniors and Pensioners Tax Offset, Medicare levy and Medicare Levy Surcharge thresholds, HECS/HELP repayment thresholds, superannuation guarantee rate and concessional caps. See the full tables on the tax rates page.
• State and territory revenue offices: transfer (stamp) duty rates, first home buyer concessions and foreign purchaser surcharges for all 8 jurisdictions. Each result on the stamp duty calculator links to the official source.
• APRA guidance: the 3 percentage point serviceability buffer lenders are required to apply when assessing home loans (APRA is the banking regulator).
• Household Expenditure Measure (HEM): the industry benchmark for minimum living expenses, scaled by household type, dependants and income, as lenders do.
• ASFA Retirement Standard: the benchmark annual budgets for a comfortable retirement used by the super calculator (ASFA is the super industry association).

Rates and thresholds were last refreshed in June 2026. Where the ATO has not yet published next year's indexed thresholds, the prior year's values are carried forward and flagged on the tax rates page.

The pay calculator and tax tracker share one engine. It works on annual figures: your gross pay is converted to an annual amount, pre-tax deductions (salary sacrifice, novated lease, work deductions) reduce taxable income, then income tax is applied bracket by bracket for your category (resident, non-resident, working holiday maker, or resident without the tax-free threshold for a second job).

Offsets (LITO, SAPTO, franking credits) reduce the tax payable. The 2% Medicare levy applies to residents, with the low-income phase-in, and the Medicare Levy Surcharge applies above the threshold when you do not hold private hospital cover. HECS/HELP repayments use the marginal system from FY2025-26 (a percentage of income above each threshold) and the flat-rate tables for earlier years, calculated on repayment income: taxable income plus reportable fringe benefits and salary-sacrificed super.

Every pay calculator result includes an expandable "How this is calculated" breakdown so you can audit each step.

The borrowing power calculator works the way lenders assess serviceability, not on rules of thumb. Salaries are converted to after-tax (net) income using the same ATO tax engine. Bonus, overtime, rental and other income are taxed at the marginal rate and then shaded to 80%, as lenders do. HECS/HELP repayments are estimated from each applicant's income at ATO rates, not as a flat percentage of the balance.

Living expenses use the higher of your declared figure and a HEM benchmark scaled by household type, dependants and income. Credit cards are assessed at 3.8% of the limit per month. The loan is then sized with a principal-and-interest annuity formula at your rate plus the 3 percentage point APRA buffer. Deposit, loan-to-value ratio (LVR), an indicative Lenders Mortgage Insurance (LMI) estimate and a maximum purchase price are derived from your savings, capped at 95% LVR.

Repayments compound at the frequency you choose (weekly, fortnightly or monthly). Extra repayments and offset balances are modelled with a period-by-period simulation of the full schedule rather than a closed-form formula, so their effect on interest and payoff time is exact for the assumptions given. Interest-only periods revert to principal-and-interest for the remaining term. Savings are measured against a clean baseline schedule with no extras and no offset.

Transfer duty uses each state and territory's published rate tables, including owner-occupier rates (VIC, QLD, WA), first home buyer exemptions and concessions, foreign purchaser surcharges, and the NT's quadratic formula. Victoria's pensioner concession is calculated; for other states the calculator shows a reminder to check the revenue office because eligibility rules vary too much to model reliably. Concession tapers (such as NSW between $800,000 and $1,000,000) are linear approximations of the official scales and are flagged as such in the results.

The super calculator projects your balance year by year to retirement: employer contributions at the super guarantee rate plus any salary sacrifice, less 15% contributions tax, with investment returns, fees, inflation and salary growth applied annually. Results are shown in both nominal dollars and today's dollars. Retirement income is estimated with a real-return drawdown to age 90 and compared against the ASFA comfortable standard.

• All results are estimates based on the inputs you provide. They are not financial, tax or credit advice.
• The pay calculator models annual tax liability. Actual PAYG withholding from each payslip follows ATO withholding schedules and can differ slightly, with the difference settled at tax return time.
• Family (combined) thresholds for the Medicare levy and Medicare Levy Surcharge are not modelled; single thresholds are used.
• Lender policies differ. Real borrowing power depends on the lender's own shading, expense treatment and credit policy. LMI premiums are banded estimates.
• Stamp duty concession tapers are linear approximations, and eligibility rules (residence periods, caps, income tests) are simplified. Always confirm with the state revenue office.
• Super projections depend heavily on assumed returns, fees and inflation; small changes compound over decades.
• Where next year's indexed thresholds are not yet published by the ATO, prior year values are carried forward and flagged.

calx is client-side software. The calculators are delivered to your browser and run there. Your salary, debts, deposit and every other figure you type stay on your device. They are never sent to a server, never stored in a database, and never visible to us. Share links encode your inputs in the link itself, so sharing is your choice. We use Google Analytics 4 for anonymous page-level usage statistics only; it never sees the numbers you enter. Read the full privacy policy.

No ads. No accounts. No selling data. calx will never carry advertising or sell your information. If calx ever introduces referral partnerships, they will be disclosed clearly and will never influence the calculator results.