Calculate GST
Pick Add GST for a price without GST, or Remove GST for a total that already includes it.
Your amount
Dollars and cents, such as 110 or 99.95.
Result
| Price excluding GST | A$100.00 |
|---|---|
| GST (10%) | A$10.00 |
| Price including GST | A$110.00 |
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Estimate only. Not tax advice. Uses the standard 10% GST; GST-free and input-taxed sales have no GST to add.
How the GST adds up
- GST is one eleventh of the totalA$110.00 ÷ 11 = A$10.00
- Take it off to get the price excluding GSTA$110.00 − A$10.00 = A$100.00
Show as a table
| Part | Sum | Amount | Share |
|---|---|---|---|
| Price excluding GST | A$110.00 − A$10.00 | A$100.00 | 90.9% |
| GST | A$110.00 ÷ 11 | A$10.00 | 9.1% |
| Price including GST | – | A$110.00 | 100% |
How to calculate GST: the formulas
Three sums cover most GST questions. Multiply by 1.1 to add GST, divide by 11 to find the GST in a total, and divide by 1.1 to get the price before GST.
| To | Do this | Example |
|---|---|---|
| Add GST to a price | Multiply by 1.1 | A$100.00 becomes A$110.00 |
| Find the GST in a total | Divide by 11 | A$110.00 contains A$10.00 |
| Remove GST from a total | Divide by 1.1 | A$110.00 becomes A$100.00 |
Source: ATO, how GST works · FY 2026–27 · checked 30 Oct 2026
Add GST to a price
Multiply the price before GST by 1.1. A quote of A$250.00 plus GST comes to A$275.00: A$250.00 for the work and A$25.00 GST. To see the GST on its own, multiply by 0.1 instead.
Remove GST from a price (reverse GST)
Divide the GST-inclusive total by 11 to find the GST, then subtract it. A receipt for A$99.95 holds A$9.09 of GST, so the price without GST is A$90.86.
Why 11 and not 10? GST is 10% of the price before GST. Add it and the total is 11 parts, one of which is GST. Taking 10% off a total gives the wrong answer: 10% of A$110 is A$11, but the GST in it is A$10.
GST-inclusive and GST-exclusive prices
| Price is | Also written | Means | Example |
|---|---|---|---|
| GST-inclusive | incl. GST | GST is already in the price | A$110.00, of which A$10.00 is GST |
| GST-exclusive | ex GST, excl. GST, plus GST | GST is still to be added | A$100.00, plus A$10.00 GST |
Use Remove GST in the calculator for a GST-inclusive amount and Add GST for a GST-exclusive one. The ATO says businesses registered for GST include it in their prices.
Source: ATO, how GST works · FY 2026–27 · checked 30 Oct 2026
How GST is rounded
For a single sale, round the GST to the nearest cent; half a cent rounds up. For an invoice with several items, the ATO describes two methods: work out GST on the invoice total and round once, or work out GST on each item, add those up and round the total. The two can give slightly different totals, and you and your customer do not have to use the same one.
This calculator uses the per-item method. Tick “Several items” to enter up to 20 lines: GST on each line is rounded to the cent, then the lines are added up. Our invoice generator rounds once on the invoice total instead, so a long invoice there can differ from this tool by a cent or two.
| Item | Excl. GST | GST | Incl. GST |
|---|---|---|---|
| Brake pads | A$100.00 | A$10.00 | A$110.00 |
| Oil and filter | A$50.50 | A$5.05 | A$55.55 |
| Wiper blades | A$18.17 | A$1.82 | A$19.99 |
| Total | A$168.67 | A$16.87 | A$185.54 |
Source: ATO, tax invoices (rounding) · FY 2026–27 · checked 30 Oct 2026
What GST is
GST (goods and services tax) is a broad-based tax of 10% on most goods, services and other items sold or consumed in Australia. Businesses registered for GST include it in their prices and claim credits for the GST in what they buy for the business. Sales that are GST-free or input-taxed have no GST to add, so this calculator does not apply to them.
Source: ATO, how GST works · ATO, GST · FY 2026–27 · checked 30 Oct 2026
The A$75,000 registration threshold
You must register for GST when your GST turnover reaches A$75,000 or more. GST turnover is your gross income minus GST. You also must register if:
- you are a new business and expect to reach A$75,000 in your first year
- you run a non-profit organisation with GST turnover of A$150,000 or more
- you provide taxi, limousine or ride-sourcing travel, whatever your turnover
- you want to claim fuel tax credits.
Otherwise registering is your choice; if you do register, you generally stay registered for 12 months. Register within 21 days of going over the threshold. You need an ABN first, and once registered you report GST on your BAS.
Source: ATO, registering for GST · FY 2026–27 · checked 30 Oct 2026
When you must give a tax invoice
If you are registered for GST and a customer asks for a tax invoice, you must give them one within 28 days. You do not have to for a sale of A$82.50 or less, including GST. A PDF or other digital invoice is fine. For a sale under A$1,000 the invoice shows:
- that the document is intended to be a tax invoice
- your identity and your ABN
- the date it was issued
- a brief description of what you sold, including quantity and price
- the GST amount, shown on its own line or, when GST is exactly one eleventh of the total, a statement such as “Total price includes GST”
- how much of each sale is taxable.
For a sale of A$1,000 or more, the invoice also shows the buyer’s identity or ABN. Our tax invoice requirements guide goes through each item, and the free invoice generator makes a PDF tax invoice with the GST worked out.
Source: ATO, tax invoices · FY 2026–27 · checked 30 Oct 2026
Common questions
Estimates only. This page gives general information, not tax advice; check your situation with the ATO or a registered tax agent.