GST Calculator Explained for Australians
Adds or removes 10% GST from any amount. This guide walks through what each input means, the formula behind the answer and a worked example using typical Australian figures. You can follow along in the free GST Calculator.
Why it matters
Australian businesses deal with GST at 10%, BAS reporting, PAYG withholding for staff, super guarantee obligations and company or individual tax depending on structure. Getting pricing and margins right is the difference between busy and profitable.
What you need to enter
The calculator asks for 1 input. The table shows each one with the example value used later in this guide.
| Input | Example value |
|---|---|
| Amount ($) | 100 |
The formula
Add GST: amount × 1.1. GST included in a price: price ÷ 11. Remove GST: price ÷ 1.1.
Worked example
Entering the example values above gives these results:
| Result | Value |
|---|---|
| Price incl. GST (add 10%) | $110.00 |
| GST to add | $10.00 |
| GST included in this amount | $9.09 |
| Price excl. GST | $90.91 |
The headline figure is $110.00 (price incl. GST (add 10%)). Change any input in the calculator and every result updates instantly, so you can test different scenarios side by side.
How the price incl. GST (add 10%) changes with amount
The table below keeps every other input at the example value and moves only “Amount ($)” up and down by 10% and 20%. It shows how sensitive the price incl. GST (add 10%) is to that one figure.
| Amount ($) | Price incl. GST (add 10%) |
|---|---|
| 80 | $88.00 |
| 90 | $99.00 |
| 100 | $110.00 |
| 110 | $121.00 |
| 120 | $132.00 |
At 80 the result is $88.00; at 120 it is $132.00. If a small change in this input moves the answer a lot, it is worth double-checking that figure before you rely on the result.
A practical tip
You must register for GST once your business turnover reaches $75,000 a year, or $150,000 for non-profits.
Keep going
Before relying on the number, read GST Mistakes Australians Make and How to Avoid Them. You might also find these guides useful:
- How the Profit Margin Calculator Works (With a Worked Example)
- Markup Calculator: Formula, Example and What the Result Means
- Using a Break-Even Calculator in Australia: A Step-by-Step Guide
Frequently asked questions
- When do I need to register for GST?
- When your annual GST turnover reaches $75,000, or $150,000 for non-profits. Taxi and ride-share drivers must register regardless of turnover.
- What company tax rate applies?
- 25% for base rate entities with turnover under $50 million, and 30% for other companies.
- Should I talk to an accountant?
- Yes, for structure, tax planning and compliance. These calculators give quick estimates only.
Run your own numbers in the GST Calculator.
Open the calculatorGeneral information only. Rates and thresholds change, usually on 1 July. Confirm current figures with the ATO or the relevant authority, and get personal advice for decisions about your situation.