Tax & government Australia
GST Calculator Australia
GST is 10% of the price before GST, which means the GST inside a GST-inclusive price is one-eleventh of it, not 10%. This calculator does both directions and rounds once, so the price, the GST and the total always agree.
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Price including GST
—Price excluding GST
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GST
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Price including GST
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The working
Working with a different rate? Edit the rates this calculator uses
These are the figures we verified on 2026-10-26. Change them to work with a historic period, or with a new rate that has been announced but which we have not published yet.
Standard 10% rate only. A calculation of the standard 10% rate. Whether GST applies to a particular sale — and whether it is GST-free or input-taxed — depends on what is sold, so confirm with the ATO or a registered tax agent for anything that matters.
How do I add or remove GST in Australia?
Australian GST is 10%. To add it, multiply the price by 1.1. To remove it from a GST-inclusive price, divide by 11 to find the GST itself, or divide by 1.1 to find the price before GST. A $1,100 price includes $100 of GST and was $1,000 before it.
Why you divide by 11 rather than take 10%
Because the 10% is added to the price before GST, the GST makes up 10 parts in every 110, which is one part in eleven. That is why the shortcut for finding the GST in a GST-inclusive price is to divide by 11, and why dividing by 10 overstates it.
The mistake is easy to make with round numbers and costly with large ones: on a $55,000 purchase, taking 10% gives $5,500 of GST when the real figure is $5,000.
When GST applies, and when it does not
GST is a broad-based 10% tax on most goods, services and other items sold or consumed in Australia. Some supplies are GST-free and some are input-taxed, and what falls into each group depends on what is being sold rather than who is selling it. A business generally has to register once its GST turnover reaches $75,000, or $150,000 for a not-for-profit organisation.
If you issue invoices, the tax invoice generator on this site checks an invoice against the ATO's requirements as you type.
How this is calculated
GST is a percentage of the price before GST. Everything else follows from that one fact.
adding GST: GST = price × 10%, total = price + GST (the same as price × 1.1)removing GST: GST = total × 1 ÷ 11, price before GST = total − GST (the same as total ÷ 1.1)the GST is rounded to the cent first and the other figures are derived from it, so they always add up
The common mistake is taking 10% off a GST-inclusive price. Ten per cent of $110 is $11, but the GST inside $110 is $10, because GST was charged on the $100 before it, not on the total. Dividing by 11 reverses the addition exactly.
The rate is editable so the calculator can handle a hypothetical or historical rate, but for any real Australian sale today the rate is 10%.
A worked example: a $1,100 GST-inclusive price
A computer is advertised at $1,100 including GST and you want to know the GST and the price before it.
- GST-inclusive price$1,100.00
- GST, one-eleventh of $1,100$100.00
- Price before GST$1,000.00
- Check: $1,000 × 10%$100.00
$100.00 of GST, and a price of $1,000.00 before it.
Going the other way, $250.00 plus 10% GST is $25.00 of GST and a total of $275.00.
The $82.50 tax invoice rule
If a customer asks for a tax invoice you must provide one within 28 days, unless the sale is $82.50 or less including GST. At or below that amount a tax invoice is not required even on request. This calculator tells you which side of the line your GST-inclusive amount falls on.
Rounding on invoices
Where an invoice has several lines, the cleanest approach is to work out GST on the taxable total once and round that single figure to the cent, rather than rounding each line and adding the results. Rounding line by line is how an invoice ends up a cent out. This tool rounds once for the same reason.
What this calculator does not do
- The standard 10% rate only; GST-free and input-taxed treatment depends on what is sold
- Does not apply the margin scheme or other special calculation rules
- Does not decide whether a business must be registered
Common 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 price, divide by 11. To find the price before GST, divide the GST-inclusive price by 1.1.
How much GST is in $1,100?
$100. One-eleventh of $1,100 is $100, so the price before GST was $1,000.
Why is it divided by 11 and not 10?
The 10% is charged on the price before GST, so GST makes up 10 of every 110 dollars of the total, one-eleventh. Taking 10% of the total removes too much.
Do I have to give a tax invoice for every sale?
Only if the buyer asks and the sale is more than $82.50 including GST, in which case you must provide it within 28 days. Sales of $82.50 or less do not need one.
When must a business register for GST?
Generally when its GST turnover reaches $75,000, or $150,000 for a not-for-profit organisation.
Where these numbers come from
- Australian Taxation Office — how Australian GST works GST is 10%; the GST in a GST-inclusive price is one-eleventh
- Australian Taxation Office — tax invoices for GST The $82.50 rule and the 28-day requirement
- business.gov.au — register for GST The $75,000 and $150,000 registration turnovers
Rates last verified 2026-10-26 Every figure the Australian Taxation Office sets is re-checked against the source at least once a year, and again whenever a change is announced. Out of date? Tell us and we will fix it.
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