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Australia GST Calculator

Find the GST inside an Australian price, or add 10% GST to a net amount. Divide by 11 for the GST, divide by 1.1 for the pre-GST price.

Runs in your browser — files never leave your device

Net
$100
GST
$10
Gross
$110

How it works

Australian GST is a flat 10% and displayed prices already include it, so the calculation most people want here is the reverse one: finding the GST inside a price they have already been quoted. Tick “amount already includes GST” and the tool divides rather than multiplying. Leave it clear to work forwards, adding 10% to a net figure — the direction you need when a tradesperson quotes ex-GST.

Because the rate is fixed, the arithmetic collapses into two shortcuts worth memorising: the GST inside a GST-inclusive price is that price divided by 11, and the price before GST is the same figure divided by 1.1. In general, net = gross ÷ (1 + rate ÷ 100) and GST = gross − net; forwards, GST = net × 0.10. Results are rounded to the cent.

Worked example. A GST-inclusive invoice of $1,347.50: GST = 1,347.50 ÷ 11 = $122.50, and the GST-exclusive amount = 1,347.50 ÷ 1.1 = $1,225.00. Feed $1,225.00 back in with the box unticked and adding 10% returns $1,347.50, confirming the two directions agree. The shortcut works just as well on small amounts: $88.00 splits into $80.00 plus $8.00 of GST, and a $4.40 coffee contains 40 cents.

One flat national rate makes Australia simpler than the United States or Canada, where the rate depends on the address. Here the only real question is whether GST applies at all. Basic food, most health services and most education are GST-free, so those prices contain no GST to extract — running a GST-free grocery total through the divide-by-11 step manufactures tax that was never charged. Set the rate to 0 for those items, or take the GST-free lines out before you calculate a mixed receipt.

The classic error is taking 10% of a GST-inclusive price. On that $1,347.50 invoice, 10% is $134.75 — $12.25 more than the $122.50 actually included — because the 10% was applied to $1,225.00, not to the total. Registered businesses need the split for a different reason: a valid tax invoice has to show the GST, and GST paid on business purchases is generally credited against GST collected from customers, so the two figures have to be recorded separately rather than kept as one gross amount.

Treat the output as an estimate — confirm whether a supply is GST-free, and how to report it, with the Australian Taxation Office or your accountant.

Other regions: United States, United Kingdom, Canada.

Frequently asked questions

How do I work out the GST in a price?
Divide the GST-inclusive price by 11. Because GST is a flat 10% added to the net figure, the tax is exactly one eleventh of the total — so $1,347.50 contains $122.50 of GST. Ticking the inclusive box on this page does the same division for you and shows all three amounts.
Why can I not just take 10% of the total?
Because the 10% was charged on the pre-GST price, not on the total. Ten per cent of a $1,347.50 invoice is $134.75, which overstates the real $122.50 by $12.25. Dividing by 11 for the GST, or by 1.1 for the pre-GST price, is the correct way to reverse it.
Which purchases are GST-free?
Basic food, most health services and most education are GST-free, so their prices contain no GST at all. Extracting 10% from those amounts would invent tax that was never charged. Set the rate box to 0 for GST-free items, and on a mixed receipt calculate only the lines that actually carried GST.
How do I find the price before GST?
Divide the GST-inclusive figure by 1.1. On a $1,347.50 invoice that gives $1,225.00 ex-GST, and the $122.50 difference is the GST. This is the number you want when a supplier quotes you inclusive but your books are kept ex-GST.
Does the GST rate vary by state or territory?
No. GST is a single national tax at a flat 10%, so unlike US sales tax or Canadian provincial taxes there is no address-based rate to look up. The only variable is whether a particular supply is taxable or GST-free.
How does the tool round?
The GST-exclusive amount, the GST and the GST-inclusive total are each rounded to the nearest cent from one input figure. Accounting systems that round GST line by line before totalling can differ by a cent or two on a long invoice, but on a single amount the results match.
Is anything I enter sent anywhere?
No. The calculation runs in your browser, so no prices or invoice amounts leave your device.

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