How to Calculate GST in Australia
Australia's Goods and Services Tax (GST) is a 10% broad-based consumption tax on most goods and services sold in Australia. Whether you're invoicing a client, pricing a product, or preparing your BAS, you need to know how to calculate GST correctly.
This guide covers the three core GST formulas — adding GST, removing GST, and extracting the GST component — with worked examples and common scenarios for Australian businesses.
Use our GST Calculator to instantly add or remove GST from any amount.
Updated: 2026
GST calculation — at a glance
- GST rate: 10% (flat rate since 1 July 2000)
- Add GST: Price × 1.1
- Remove GST: Price ÷ 1.1
- GST component only: Price ÷ 11
- Registration threshold: $75,000 annual turnover ($150,000 for non-profits)
The GST formula explained
There are three variations of the GST formula, depending on what you're trying to calculate. All three are based on the 10% rate — the only GST rate in Australia.
1. Adding GST to a price
To calculate the GST-inclusive price, multiply the GST-exclusive amount by 1.1:
GST-inclusive price = Price (ex GST) × 1.1
This works because GST is 10% of the ex-GST price. Multiplying by 1.1 adds 10% in a single step.
2. Removing GST from a price
To find the GST-exclusive price from a GST-inclusive amount, divide by 1.1:
GST-exclusive price = Price (inc GST) ÷ 1.1
This reverses the addition — dividing by 1.1 strips the 10% GST component from the total price.
3. Finding the GST amount only
To extract just the GST component from a GST-inclusive price, divide by 11:
GST amount = Price (inc GST) ÷ 11
Why 11? Because the GST-inclusive price contains 11 parts — 10 parts for the ex-GST price and 1 part for the GST. Dividing by 11 isolates that 1 part.
GST calculation examples
Example 1: Adding GST to an invoice
A web designer charges $3,000 for a project (ex GST). They need to issue a tax invoice with GST:
| Calculation | Result |
|---|---|
| Subtotal (ex GST) | $3,000.00 |
| GST ($3,000 ÷ 10) | $300.00 |
| Invoice total (inc GST) | $3,300.00 |
Example 2: Removing GST from a receipt
A business buys office equipment for $880 inc GST. They need the GST-exclusive amount for their bookkeeping and the GST amount for their BAS:
| Calculation | Result |
|---|---|
| Total paid (inc GST) | $880.00 |
| GST amount ($880 ÷ 11) | $80.00 |
| Price ex GST ($880 ÷ 1.1) | $800.00 |
Example 3: Working out GST for a BAS
A small business had $55,000 in sales (inc GST) and $22,000 in business purchases (inc GST) during the quarter:
| BAS Line | Amount |
|---|---|
| GST on sales ($55,000 ÷ 11) | $5,000.00 |
| GST on purchases ($22,000 ÷ 11) | $2,000.00 |
| Net GST payable to ATO | $3,000.00 |
The business owes the ATO the difference between GST collected on sales and GST paid on purchases.
Common GST calculation scenarios
| Scenario | Ex GST | GST | Inc GST |
|---|---|---|---|
| Freelancer invoicing $2,000 | $2,000 | $200 | $2,200 |
| Retail sale of $49.95 inc GST | $45.41 | $4.54 | $49.95 |
| Contractor quote $15,000 | $15,000 | $1,500 | $16,500 |
| Monthly rent (commercial) $5,500 | $5,000 | $500 | $5,500 |
| Office supplies $330 inc GST | $300 | $30 | $330 |
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GST registration threshold
You must register for GST if your business has a current or projected GST turnover of $75,000 or more per year. For non-profit organisations, the threshold is $150,000. Taxi drivers and ride-sharing drivers must register regardless of their turnover.
Voluntary registration
If your turnover is below the threshold, you can still choose to register for GST. This allows you to claim input tax credits on business purchases, which can be beneficial if you regularly buy from GST-registered suppliers.
What you must do once registered
Once registered, you must include GST in the price of most goods and services you sell, issue tax invoices when requested, lodge Business Activity Statements (BAS) — usually quarterly — and pay the net GST amount to the ATO.
Input tax credits
As a registered business, you can claim credits for GST included in the price of goods and services you buy for your business. These credits are offset against the GST you collect on sales, reducing what you owe the ATO.
GST-free vs input taxed vs taxable sales
Not everything attracts GST. Australian tax law classifies sales into three categories, each with different GST treatment:
| Type | GST Treatment | Examples |
|---|---|---|
| Taxable | 10% GST applies | Most goods & services, commercial rent, consulting fees |
| GST-free | No GST charged | Fresh food, medical services, education, exports |
| Input taxed | No GST charged, no input tax credits | Financial supplies (loans, share trading), residential rent |
The key difference between GST-free and input taxed: with GST-free sales you can still claim input tax credits on related purchases; with input taxed sales you cannot.
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