How to calculate GST in Australia
Australia's Goods and Services Tax (GST) is a flat 10% on most goods and services. The maths is simple once you know which direction you're going — this calculator does both, but here's what's happening under the hood.
Adding GST to a price
If you have a price that excludes GST and want the GST-inclusive total, multiply by 1.1:
- GST amount = price × 10% (e.g. $200 × 0.10 = $20)
- Total including GST = price × 1.1 (e.g. $200 × 1.1 = $220)
Removing GST from a total
If you have a GST-inclusive total and want to find the GST portion, divide by 11 — not by 10. This trips a lot of people up:
- GST included = total ÷ 11 (e.g. $220 ÷ 11 = $20)
- Price before GST = total ÷ 1.1 (e.g. $220 ÷ 1.1 = $200)
Why one-eleventh? Because the 10% was added to the smaller pre-GST figure, so GST is 1/11th of the grossed-up total, not 1/10th.
Need this on a compliant tax invoice with GST shown correctly? The Australian invoice generator calculates GST both ways (inclusive or exclusive) and lays out an ATO-ready tax invoice for free.
Do you need to charge GST?
You must register for GST once your GST turnover reaches $75,000 a year (or from day one if you drive a taxi or ride-share). Below that, registering is optional. Once registered, you charge 10% GST and issue tax invoices. Not registered? You issue plain invoices with no GST. There's more detail in our guide to the GST registration threshold and the tax invoice requirements.
Frequently asked questions
How do I calculate GST in Australia?
To add GST, multiply the price by 1.1. To find the GST inside a GST-inclusive total, divide the total by 11. To get the price before GST, divide the total by 1.1.
How do I remove GST from a total?
Divide the GST-inclusive amount by 11 to get the GST portion, then subtract it from the total for the GST-exclusive price. $110 includes $10 GST and $100 before GST.
What is the GST rate in Australia?
10%, applied to most goods and services. Some items are GST-free, such as basic food and certain health and education services.
Do I need to charge GST?
Only once your GST turnover reaches $75,000 a year (or from day one for taxi and ride-share drivers). Below that, registration is optional.
General information, not tax advice — check the ATO for your situation.