GST calculator (Australia): add or remove 10% GST
Enter an amount and choose whether it already includes GST. You'll see the GST-exclusive amount, the GST and the GST-inclusive amount, rounded to the cent. Further down: a whole list line by line, working back from a GST amount, worked examples and answers to common questions.
Everything runs in your browser. Nothing you type is sent anywhere or saved. Rates and rules checked against the ATO on 17 Oct 2026.
Several amountsKnow only the GSTHow it's worked outWorked examplesWhen GST appliesFAQSources
Several amounts, line by line
Paste a list (one amount per line, optionally with a label, e.g. Cable 189.50) to get the GST on each line and the totals. Handy for receipts, a quote's line items or a quarter's purchases.
Know only the GST amount?
How GST is worked out
The rate is 10%. GST is a 10% tax on most goods, services and other items sold or consumed in Australia.
- Adding GST: GST = 10% of the GST-exclusive price, so the GST-inclusive price is the GST-exclusive price × 1.1.
- Removing GST (the divide-by-11 rule): the GST in a GST-inclusive price is the price ÷ 11. The GST-exclusive price is what's left (the same as dividing by 1.1).
- Common mistake: taking 10% off a GST-inclusive price. 10% of $110 is $11, but the GST in $110 is $10 ($110 ÷ 11).
Rounding: for an invoice with one taxable sale, the ATO says to round GST to the nearest cent, rounding half a cent up. This calculator does that. Invoices with several taxable sales have their own rounding rules (see the ATO tax invoices page), so a line-by-line total can differ by a cent or two from GST worked out on the grand total. The list calculator above shows both.
Worked examples
| Situation | Working | GST | Total |
|---|---|---|---|
| 1. A quote. An electrician quotes $2,400 + GST for a switchboard upgrade. | $2,400 × 10% = $240 | $240.00 | $2,640.00 |
| 2. A receipt. $82.50 of fixings from a hardware store, GST included. | $82.50 ÷ 11 = $7.50; $82.50 − $7.50 = $75.00 before GST. At $82.50 or less you can claim the credit without a tax invoice, but keep the receipt. | $7.50 | $82.50 |
| 3. A mixed-use bill. A $99 phone bill (GST included), used 60% for the business. | GST in the bill: $99 ÷ 11 = $9.00. GST credit you can claim: 60% × $9.00 = $5.40 | $5.40 claimable | $99.00 |
| 4. A credit note. You refund a customer $330 including GST. | −$330 ÷ 11 = −$30. It reduces the GST on your sales (1A) for the period. | −$30.00 | −$330.00 |
| 5. Line-by-line rounding. Three items at $19.99 each, GST included. | Each line: $19.99 ÷ 11 = $1.8172… → $1.82, so 3 × $1.82 = $5.46. On the total: $59.97 ÷ 11 = $5.4518… → $5.45 | $5.46 or $5.45 | $59.97 |
| 6. Working back. A supplier invoice shows only "GST $45.00". | $45 × 10 = $450 before GST; $45 × 11 = $495 including GST | $45.00 | $495.00 |
When does a price include GST?
If you're registered for GST, or required to be, the goods and services you sell in Australia are taxable (GST is in the price) unless they're GST-free or input-taxed.
You must register for GST:
- when your GST turnover (gross business income minus GST) is A$75,000 or more, counting the current month and the previous 11 months, or when your projected turnover for the current month and the next 11 months is likely to reach A$75,000 (A$150,000 for non-profit organisations). Check yours with the GST registration checker.
- if you provide taxi or limousine travel for passengers, including ride-sourcing (rideshare), whatever your turnover
- in some other cases, such as some sharing-economy and digital-platform income, or to claim fuel tax credits.
Once you're required to register, you have 21 days to do it. Otherwise registering is optional.
Not every sale includes GST. Some things are GST-free, including most basic food, some education courses and some medical, health and care services, as well as exports and others on the ATO list. Input-taxed sales, such as residential rent and financial supplies, have no GST in the price either. Don't use this calculator to add GST to those sales.
The A$82.50 tax invoice threshold. If a customer asks for a tax invoice, you must give them one within 28 days unless the sale is A$82.50 (including GST) or less. Buyers need a tax invoice to claim a GST credit for a purchase that cost more than A$82.50 (including GST). Need invoice numbers? Try the invoice number generator, or the quote template for quotes with GST shown properly.
GST calculators by trade
Same maths, with examples and invoice tips for your work: electricians · plumbers · carpenters · painters · cleaners · landscapers · photographers · rideshare drivers · all guides
Frequently asked questions
How do I calculate GST in Australia?
To add GST, multiply the GST-exclusive price by 1.1 (the GST is 10% of the price). To find the GST in a GST-inclusive price, divide it by 11; the GST-exclusive price is what's left. For example, $550 including GST contains $50 GST ($550 ÷ 11) and $500 before GST.
Why divide by 11 instead of taking 10% off?
Because the 10% is charged on the GST-exclusive price. A $110 price is $100 plus $10 GST, so the GST is one-eleventh of $110, not 10% of it. Taking 10% off $110 gives $11, which overstates the GST by $1.
Do I charge GST if I'm not registered?
No. If you're not registered for GST you can't include GST in your prices or issue tax invoices. You must register within 21 days once your GST turnover reaches $75,000 (current or projected), or straight away if you drive taxi or rideshare.
When do I have to give a tax invoice?
If a customer asks for one, you must give them a tax invoice within 28 days, unless the sale is $82.50 or less including GST. Your customer needs a tax invoice to claim a GST credit for purchases over $82.50.
Can I claim the GST on business purchases?
If you're registered for GST, you can generally claim a GST credit for the GST in the price of things you buy for your business. You claim only the business share of mixed-use purchases, and you need a tax invoice for purchases over $82.50 including GST.
How is GST rounded?
For an invoice with a single taxable sale, the ATO says to round the GST to the nearest cent, with half a cent rounded up. This calculator does that. Invoices with several taxable sales have their own rounding rules, so totals worked out line by line can differ by a cent or two.
Does every sale include GST?
No. GST-free sales include most basic food, some health, medical, education and care services, and exports. Input-taxed sales, such as residential rent and financial supplies, don't include GST either. Check the ATO lists before adding GST to these.
Which GST figures go on my BAS?
On Simpler BAS (most small businesses), you report total sales at G1, the GST on your sales at 1A and the GST credits on your purchases at 1B. The amount you pay or get back is 1A minus 1B.
Sources
Checked 17 Oct 2026: ATO Goods and services tax (GST) (the 10% rate); When you can claim a GST credit (divide by 11; the A$82.50 rule for claiming credits); Tax invoices (28 days, A$82.50, rounding); Taxable sales; Registering for GST (A$75,000 threshold, taxi and ride-sourcing, 21 days); GST-free sales; Input-taxed sales.
General information, not tax advice. It doesn't take your circumstances into account. Check with the ATO or a registered tax agent before relying on it.
Related
- Free tools: BAS due dates FY2026-27 · Sole trader tax calculator · Do I need to register for GST? · Invoice reminder emails · all tools
- Article: Tax invoice vs invoice in Australia: what must be on it
- Article: BAS G1, 1A and 1B explained for sole traders, with a worked example
- Want the GST on a whole quarter of sales and purchases added up for your BAS? GST & BAS Workbook FY2026-27 (paid spreadsheet)