GST Calculator (Australia)

Add 10% GST to a price, or work out how much GST is inside a GST-inclusive total. Free, instant, and accurate to the cent.

How GST is calculated

Australian GST is 10%. To add GST to a price, multiply by 1.1 — a $100 service becomes $110 including GST.

To find the GST inside a total, divide the GST-inclusive amount by 11 (the “1/11th rule”). A $110 total contains $10 of GST, so the GST-exclusive price is $100.

When do I need to charge GST?

You generally must register for GST once your business turnover reaches $75,000 a year (or from day one for taxi and ride-share drivers). Once registered, you charge 10% GST on taxable sales, issue tax invoices, and report the GST on your BAS. Below the threshold, registering is optional. When in doubt, check with your accountant or the ATO — this calculator is a tool, not tax advice.

What has to be on a tax invoice?

For sales of $82.50 or more (including GST), a valid tax invoice needs: the words “Tax invoice”, your identity and ABN, the date, a description of what was sold, and the GST amount (or a statement that GST is included in the price).