Excluding GST
$1,000.00
GST
$100.00
Including GST
$1,100.00
How GST is calculated in Australia
GST is 10%, so the arithmetic is simpler than it looks, but the two directions are not symmetrical, which is where most mistakes happen.
- To add GST to a GST-exclusive price, multiply by 1.1. $1,000 becomes $1,100.
- To find the GST inside a price that already includes it, divide by 11. The GST in $1,100 is $100, not $110, which is what you get if you take 10% off the total by mistake.
- To get back to the exclusive price, divide the inclusive price by 1.1.
How much is GST on common amounts?
Worked both ways, so you can check the direction you need at a glance. The left column is a price before GST; the right is a total that already includes it.
| Amount | Add GST, total becomes | GST inside that amount |
|---|---|---|
| $50.00 | $55.00 | $4.55 |
| $100.00 | $110.00 | $9.09 |
| $500.00 | $550.00 | $45.45 |
| $1,000.00 | $1,100.00 | $90.91 |
| $5,000.00 | $5,500.00 | $454.55 |
The right-hand column is the one worth remembering: the GST inside $1,100 is $100, not $110. Dividing by 11 gets you there in one step.
When there is no GST to calculate
Two situations produce a nil GST figure, and they are not the same thing:
- You are not registered for GST. Then you do not charge it at all, whatever you are selling. Registration is compulsory once your GST turnover reaches $75,000 in a rolling twelve-month period, and optional below that.
- The supply is GST-free. You are registered, but this particular item carries no GST. Most basic food, many health and education services, and exports are GST-free. You still report the sale, and you can still claim GST credits on what you bought to make it.
A third case catches people out: input taxed supplies, such as residential rent and most financial services. No GST is charged, and unlike GST-free supplies you cannot claim credits on the related purchases either.
Where these numbers go on your BAS
The GST you charge customers is what you report at 1A and owe the ATO. The GST you were charged on business purchases is what you claim back at 1B. You remit the difference. Our explainer on what a BAS is walks through each label, and Balaana tallies both figures as you invoice and spend.
Frequently asked questions
Divide the GST-inclusive total by 1.1 to get the price excluding GST, or divide it by 11 to get the GST amount directly. Subtracting 10% from the inclusive figure gives the wrong answer: the GST in $110 is $10, not $11.
To add GST, multiply the price by 1.1. To find the GST inside a total that already includes it, divide by 11. To get back to the price before GST, divide the total by 1.1. Those three cover every GST calculation at a 10% rate.
The rate has been 10% since GST began in 2000. Some supplies are GST-free instead, including most basic food, many health and education services, and exports, which means no GST is charged on them at all rather than a lower rate.
No. You must not charge GST unless you are registered for it. Registration is compulsory once your GST turnover reaches $75,000 in a rolling twelve-month period, and optional below that.
No. The calculator runs entirely in your browser and nothing is transmitted. The figures appear in the page URL so you can bookmark or share a calculation, and that URL never leaves your device unless you send it to someone.