PennyCompass

Australia GST Calculator

Free Australia GST calculator. Add or extract 10% Goods and Services Tax from any amount.

Published

Written by PennyCompass Team

10% GST inclusive or exclusive.

Total with GST

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GST

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Pre-GST

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Worked example

Take a pre-GST price of $100 and add 10 percent GST. The GST is $100 times 0.10, which is $10, so the GST-inclusive total is $110. Now run it the other way. Starting from a $110 GST-inclusive total and extracting the tax, you divide $110 by 1.1 to get the pre-GST amount of $100, and the GST portion is the $10 difference. A handy shortcut for the extraction case is that the GST is always one eleventh of any GST-inclusive amount, because $110 divided by 11 is $10. Both directions agree, which is the check a BAS preparer relies on.

DirectionPre-GSTGSTTotal

How it is calculated

Australian GST is a flat 10 percent on most goods and services. In add mode the calculator multiplies the pre-tax amount by 10 percent to get the GST, then adds it to give the inclusive total. In extract mode it works backwards from a GST-inclusive figure by dividing by 1.1 to recover the pre-tax base, and the GST is whatever is left over. The reason the GST is one eleventh of an inclusive price, rather than one tenth, is that the 10 percent was added to the smaller pre-tax base, so as a share of the larger total it shrinks to 1 divided by 11. Figures are rounded to the cent. Some items such as basic food, health, and education are GST-free, so apply this only to taxable supplies.

Frequently asked questions

Inclusive vs exclusive?
Inclusive: total amount already includes GST, divide by 11 to extract the GST portion (because the GST is 1/11th of inclusive). Exclusive: pre-tax amount, multiply by 10% to add GST.
Which goods and services are GST-free in Australia?
The ATO exempts several categories from GST including most basic foods, many health and medical services, certain educational courses, and childcare. Exports of goods and services to overseas customers are also GST-free. Always check the ATO website or consult a tax professional to confirm whether a specific supply is taxable or exempt.
When do I need to register for GST?
You must register for GST if your business has a GST turnover of $75,000 or more in any 12-month period, or $150,000 for non-profit organisations. Taxi, limousine, and ride-sharing drivers must register regardless of turnover. Once registered, you lodge a Business Activity Statement (BAS) to report and pay GST collected.
How do I claim GST credits (input tax credits)?
If you are registered for GST, you can claim credits for the GST included in the price of goods and services you purchase for your business. You claim these on your BAS by recording creditable acquisitions. You generally need a valid tax invoice from the supplier for purchases over $82.50 to support your claim.

Related calculators

Income Tax

PAYG.

Sources

  1. ATO — Individual Income Tax Rates 2026-27, Australian Taxation Office
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