GST Calculator: Add or Remove GST
In Canada? GST/HST Calculator (Canada)In the US? Sales tax calculator
How to add or remove GST
Adding GST: multiply the GST-exclusive price by 1.1. For example, $1,000.00 plus GST is $100.00 of GST and $1,100.00 in total.
Removing GST (the 1/11 rule): the GST in a GST-inclusive price is the price divided by 11, and the GST-exclusive price is the rest. For example, $110.00 including GST holds $10.00 of GST and $100.00 excluding GST; $1,000.00 including GST holds $90.91 of GST and $909.09 excluding GST.
That is the Act's own arithmetic: GST is 10% of the value of a taxable supply (s 9-70), and the value is the price × 10/11 (s 9-75). The Act's example is a car sold for $22,000, which carries $2,000 of GST.
In Invoice lines mode, the calculator adds up the lines at each rate, works out the GST once per rate and shows the GST-exclusive amount, the GST and the GST-inclusive amount per rate and in total.
Rounding to the cent
Section 9-90 of the GST Act rounds the GST on a single taxable supply on an invoice to the nearest cent, rounding 0.5 cents upwards. When an invoice records two or more taxable supplies, one allowed method is to work out the GST on each supply without rounding, add the amounts up and then round the total to the nearest cent.
This calculator follows that method: every result is rounded to the nearest cent (half a cent up), and in invoice-line mode the lines are added up first and rounded once. Section 9-90 also allows a line-by-line method, so an accounting system can sometimes differ by a cent.
Is everything taxed at 10%?
GST is a broad-based tax of 10% on most goods, services and other items sold or consumed in Australia. Some supplies are GST-free or input taxed, so check with the ATO how GST applies to what you sell.
You must register for GST when your GST turnover is $75,000 or more ($150,000 or more for non-profit organisations), or when you provide taxi travel, including ride-sourcing.
GST calculator questions
Is GST 10% or 11% in Australia?
GST is 10% of the price before GST. Because the GST is then part of the price, it makes up 1/11 of a GST-inclusive price, or about 9.09%. That is where the "divide by 11" rule comes from; the rate itself is 10%.
How much GST is on $1,000?
If $1,000.00 excludes GST, the GST is $100.00 and the total is $1,100.00. If $1,000.00 already includes GST, the GST is $1,000.00 ÷ 11 = $90.91 and the price excluding GST is $909.09.
How do I calculate GST?
To add GST, multiply the price by 1.1. To find the GST in a GST-inclusive price, divide it by 11; subtract that GST to get the price excluding GST.
How is GST rounded?
Under section 9-90 of the GST Act, the GST on a single taxable supply on an invoice is rounded to the nearest cent, with 0.5 cents rounded up. For several supplies on one invoice, you can add up the unrounded GST and round the total, which is what this calculator does.
When do I have to register for GST?
Generally when your business's GST turnover is $75,000 or more, or $150,000 or more for a non-profit organisation, and always if you provide taxi travel or ride-sourcing.
Can I calculate New Zealand GST or another rate?
Yes. Choose Other rate and type the percentage, for example 15. The calculator then adds or removes that rate in the same way.
Are my amounts saved or sent anywhere?
No. The calculation runs in your browser. Amounts and any rate you type yourself are not put in the page address or in analytics, which only count actions such as adding or removing GST.
Sources
We checked the rate and the rounding rule in the GST Act and on business.gov.au. This calculator is not tax advice. Checked 9 October 2026.