Australian GST Component Calculator

Pull the GST out of any Australian GST-inclusive price. The standard GST rate is 10%, so the GST component of an inclusive amount is one-eleventh of that total.

Formula

GST component = GST-inclusive amount ÷ 11. The same calculation can be written as inclusive amount × 10 ÷ 110.

Examples

For A$110 including GST, GST is A$10 and the GST-exclusive amount is A$100. For A$550 including GST, GST is A$50 and the GST-exclusive amount is A$500.

Why the one-eleventh rule works

A GST-inclusive price is the original price plus 10% GST, so the total is 110% of the GST-exclusive amount. The GST slice of that total is 10 out of 110, which simplifies to one-eleventh.

Worked example: a Canberra retailer’s price split

A Canberra retailer advertises a coffee machine for $330 including GST. The GST component is $330 ÷ 11, which is $30. The GST-exclusive price is $300. When she does her BAS, she reports $300 of sales and $30 of GST collected for that machine. If she sells 20 machines in a quarter, that is $6,000 of sales and $600 of GST collected. Try $330 in the calculator above and you will see GST of A$30.00 and a before-GST figure of A$300.00. To add GST going the other way, use the GST on invoice calculator.

Use this for

• Checking a retail price that includes GST
• Separating GST before bookkeeping
• Checking an invoice total
• Estimating the GST portion of a taxable sale

Practical tips for splitting prices in your books

Split every GST-inclusive total into its GST and ex-GST parts before entering it in your accounting software, because the BAS wants the two figures separately. Watch out for mixed dockets: a $330 total that includes a GST-free item needs each line split on its own treatment, not the whole docket divided by 11. Keep the one-eleventh rule in your head for quick checks at the shops, and use the calculator above for exact figures. When the split feeds into a credit claim, the GST credit calculator picks up from here.

Limitations

This calculator does the maths only. It cannot tell you whether an item is taxable, GST-free or input-taxed. Special GST rules should be checked separately.

Frequently asked questions

Why divide by 11 instead of subtracting 10%?

Because the 10% GST was calculated on the GST-exclusive price, not on the total you see. Dividing the total by 11 reverses the original calculation exactly.

Does the one-eleventh rule work for GST-free items?

No. GST-free and input-taxed supplies have no GST in the price, so there is nothing to extract.

How should I handle rounding?

Round the GST component to the nearest cent. The ex-GST figure is the total minus the rounded GST.

Can I use this for imported goods?

Imports follow different GST rules, including deferred GST arrangements, so check the ATO guidance for imports rather than using this simple split.

Australian GST Calculator · GST Inclusive vs Exclusive Calculator · ATO