How our calculators work

This page explains the formulas, assumptions and official sources behind every CalculatorQuest calculator, so you can check any result yourself. Tax figures are current for the 2026-27 financial year and were last checked against the ATO on 12 October 2026.

Estimates only, not tax or financial advice. Results are general information based on published ATO rules and the figures you enter. For advice about your situation, speak to a registered tax agent or licensed financial adviser. How we calculate · Spotted a mistake?

How figures are kept

Every tax, Medicare, HELP, super and termination figure lives in a single configuration file, one entry per financial year, with the official source URL recorded beside it and the date it was last checked. Calculators and articles read from that file; they do not keep their own copies of rates.
If the ATO has not yet published a figure for a year, we do not estimate it. We either reuse the latest published figure and say so on the page, or leave the feature out.
Automated tests check the tax brackets, LITO, Medicare levy, MLS, HELP, super guarantee and redundancy calculations at their thresholds against amounts worked out by hand from the ATO tables. Another test flags any financial year typed directly into a page instead of coming from the configuration.
Calculations run in your browser. The numbers you enter are not sent to us.

Pay, salary and tax refund calculators

Used by the pay calculator, salary after tax tables, tax refund estimator and the salary articles.

Pay is converted to an annual amount: weekly × 52, fortnightly × 26, monthly × 12.
Taxable income = gross pay − any salary sacrifice into super.
Income tax is worked out on taxable income with the resident tax rates (table below).
The low income tax offset (LITO) is subtracted: $700 up to $37,500, reducing by 5 cents per dollar to $45,000, then by 1.5 cents per dollar until it reaches $0 at $66,667. It cannot reduce tax below $0.
The Medicare levy is 2% of taxable income. There is no levy on taxable income of $28,011 or less, and up to $35,013 it is 10 cents per dollar above $28,011(single person, not entitled to the seniors and pensioners tax offset). The ATO has not yet published 2026-27 low-income Medicare levy thresholds, so the 2025-26 thresholds are used.
The Medicare levy surcharge (MLS) is added only when you say you do not have private hospital cover. Its tier is set by taxable income plus salary-sacrificed super. The salary tables and articles assume you have hospital cover and show the MLS separately.
If you tick HECS-HELP, the compulsory repayment is worked out on repayment income (taxable income plus salary-sacrificed super) as described in the HECS-HELP section.
Employer super is 12% of ordinary time earnings, up to the maximum contribution base of $270,830 a year. Overtime is not treated as ordinary time earnings. Super is paid on top of the salary you enter.
Take-home pay = gross pay − salary sacrifice − income tax − Medicare levy − MLS − HELP repayment. Results are rounded to the nearest dollar.

Resident income tax rates 2026-27
Taxable income	Tax on this income
$0 – $18,200	Nil
$18,201 – $45,000	15c for each $1 over $18,200
$45,001 – $135,000	$4,020 plus 30c for each $1 over $45,000
$135,001 – $190,000	$31,020 plus 37c for each $1 over $135,000
$190,001 and over	$51,370 plus 45c for each $1 over $190,000

Assumptions. You are an Australian resident for tax purposes for the whole year, single, with no dependants, no other income, no deductions and no tax offsets other than the LITO. Your actual tax is worked out by the ATO when you lodge your return.

Tax refund estimator. Refund = tax withheld − (income tax after LITO + Medicare levy) on the salary you enter. It does not include deductions, other income or offsets, so treat it as a starting point.

HECS-HELP calculators

Since 1 July 2025 compulsory repayments are marginal: you repay a percentage of repayment income above the threshold, not of your whole income. For 2026-27:

No repayment on repayment income of $69,528 or less.
$69,529 – $129,717: 15c for each $1 over $69,528.
$129,718 – $186,050: $9,028 plus 17c for each $1 over $129,717.
Above $186,050: 10% of total repayment income.

Repayment income is taxable income plus reportable fringe benefits, reportable super contributions (including salary sacrifice), net investment losses and exempt foreign employment income. The calculators include taxable income and salary sacrifice only.

The indexation calculator applies the rate set each 1 June to the part of the debt more than 11 months old. The 2026 rate was 2.8%.

Super, salary sacrifice and retirement

Salary sacrifice. Each sacrificed dollar is taken out of taxable income and taxed at 15% in the fund instead. If income plus concessional contributions is over $250,000, Division 293 tax adds 15% on the lower of the contributions and the excess. The concessional cap for 2026-27 is $32,500, including employer super.
Retirement projections. Your current balance grows at the annual return you enter, and monthly contributions are compounded monthly. The calculator inflates your target income by the inflation rate you enter, subtracts any Age Pension or other income you enter, and compares the rest with 4% of the projected balance. The 4% figure is a planning rule of thumb, not a guarantee or an official rate. Fees, insurance premiums and taxes inside the fund are not modelled unless you reduce the return to allow for them.
We do not work out Age Pension entitlements; see Services Australia.

Contractor, overtime and redundancy

Contractor tax. Taxable income = income − business expenses, taxed with the resident rates, LITO and Medicare levy above (MLS not included). If income is $75,000 or more, GST of 10% is shown on income and expenses, treating the amounts you enter as GST-exclusive. Quarterly PAYG instalments are shown as a quarter of the annual tax; the ATO sets your actual instalment amount.
Overtime. Overtime pay = hourly rate × multiplier × hours. The multipliers offered (1.5×, 2×, 2.5×) are common award rates; your award or agreement sets yours (check Fair Work).
Redundancy. The tax-free part of a genuine redundancy payment is $13,598 plus $6,801 for each completed year of service (2026-27). The rest is treated as an employment termination payment, taxed at 32% (under preservation age) or 17% (at or over) up to the $270,000 cap and 47% above it. Rates include the Medicare levy. The whole-of-income cap and unused leave are not modelled.

Property and investment calculators

Mortgage and loan repayments use the standard amortisation formula: repayment = P × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1), where P is the loan, r the interest rate per period and n the number of repayments. Fees and rate changes are not included.
Stamp dutyuses each state's published transfer duty scale for an owner-occupied purchase. We are re-checking every state's scale and concession against its revenue office; until a state's page shows its source and verified date, treat the result as indicative and confirm with the revenue office.
Rental yield.Gross yield = weekly rent × 52 ÷ property value. Net yield subtracts the expenses and loan repayments you enter. "Total return" adds an assumed 3% a year capital growth, which is an assumption, not a forecast.
Negative gearing. Tax saved = (income tax + Medicare levy on your salary) − (the same on salary minus the net rental loss), using the 2026-27 rates.
Capital gains tax. Gain = sale price − purchase price − costs. Individuals who held the asset for at least 12 months get a 50% discount; the taxable gain is added to your income and taxed at 2026-27 rates.
Novated lease. A simplified estimate: GST credit on the price (limited to the car limit of $69,883), minimum residual value for the lease term, running costs, and the employee contribution method for FBT. Electric cars under the luxury car tax threshold for fuel-efficient vehicles ($91,661) are treated as FBT-exempt. Interest, fees and insurance are not included.
Compound interest uses A = P(1 + r/n)^nt, where n is the number of compounding periods a year. The savings and investment calculators compound monthly and add your monthly deposits at the end of each month.

Other tools

Date, unit, maths, health and education tools use standard published formulas (for example BMI = weight in kg ÷ height in metres squared). They are not tax tools and are not part of the rate checks above. Health results are general information, not medical advice.

Data sources

Every rate and threshold used on the site comes from one of these official pages:

How and when figures are updated

When the ATO publishes rates for a new financial year, we add that year to the configuration, check every figure against its source and record the date. Each calculator and article shows that "last updated" date and links to its sources.
When legislation changes during a year, we update the affected figures and articles the same way. Changes that are law but not yet in effect (such as the negative gearing and CGT changes from 1 July 2027) are described on the relevant pages but not used in calculations until they start.
Articles show the date their content last changed. Fixing a link or a typo does not change that date; correcting a figure does.
Currently configured financial years: 2026-27 (checked 12 October 2026), 2025-26 (checked 12 October 2026). The default is 2026-27.

Reporting errors

If a result or figure looks wrong, please tell us. Use the Spotted a mistake? link at the bottom of every page, or email contact@calculatorquest.com.au with the page, the numbers you entered, what you expected and, if you have one, the official source.

We check each report against the official source. If we were wrong, we fix the figure in the configuration (which corrects every page that uses it) and update the affected articles' "last updated" date.