Free GST Calculator for Australian Businesses
Add or remove 10% GST from any amount in seconds. Built for Australian businesses preparing invoices, quotes and BAS.
Last updated 31 May 2026
This free GST calculator works out the goods and services tax on any amount using the standard Australian rate of 10%. Enter a figure and choose whether to add GST to a GST-exclusive amount or remove GST from a GST-inclusive total. The calculator instantly shows the GST component, the amount excluding GST and the amount including GST, so you can price a job, raise a tax invoice or check a supplier bill without reaching for a spreadsheet. Every figure is formatted in Australian dollars and rounded to the cent, matching how the Australian Taxation Office expects GST to be shown on a tax invoice.
How to use this tool
- 1
Enter the amount
Type the dollar figure you want to work with, such as a quote, invoice line or supplier bill.
- 2
Choose add or remove
Select "Add GST" if your figure excludes GST, or "Remove GST" if it already includes the 10% tax.
- 3
Read the result
The calculator shows the GST component, the GST-exclusive amount and the GST-inclusive total instantly.
How GST works in Australia
Goods and services tax is a broad-based tax of 10% on most goods, services and other items sold or consumed in Australia. If your business is registered for GST, you add 10% to the price of your taxable sales and pass that GST on to the Australian Taxation Office, usually through your quarterly business activity statement. You can also claim back the GST you pay on business purchases, known as a GST credit. The net amount you owe is the GST you collected on sales minus the GST credits on your purchases. Because the rate is a flat 10%, the maths is simple, but it is easy to make rounding mistakes when you are doing it by hand across dozens of invoices each month.
Adding GST versus removing GST
There are two everyday calculations. Adding GST takes a GST-exclusive figure and increases it by 10%, so a 100 dollar service becomes 110 dollars including GST. Removing GST takes a GST-inclusive total and works backwards to find the original price and the tax component. To remove GST you divide the total by 1.1, not by 0.9, which is the most common error business owners make. For example, a 110 dollar inclusive total divided by 1.1 gives 100 dollars excluding GST and 10 dollars of GST. This calculator handles both directions so you never have to remember which way to divide.
When your business must register for GST
Most businesses must register for GST once their annual turnover reaches 75,000 dollars, or 150,000 dollars for non-profit organisations. Taxi, ride-share and limousine drivers must register regardless of turnover. Once registered, you must show GST on your tax invoices, lodge activity statements and keep records that support the GST credits you claim. If your turnover is below the threshold you can still register voluntarily, which can make sense if you buy a lot of GST-inclusive stock or equipment. Knowing your GST position helps you price correctly so the tax does not quietly eat into your margin.
Getting GST right on every invoice
A valid tax invoice for sales of 1,000 dollars or more must show the seller identity and ABN, the date, a description of what was sold, the GST amount (or a statement that the total includes GST) and the buyer identity or ABN. Getting these details wrong can delay payment and create headaches at BAS time. Many Australian businesses still calculate GST by hand or in a spreadsheet, then re-key the same figures into accounting software, which doubles the work and the error rate. The calculator above removes the manual step, and if you find yourself repeating this across hundreds of transactions, that is a strong signal the whole invoicing and BAS workflow is ready to be automated.
Worked example
A consultant quotes a 2,500 dollar project excluding GST and wants the GST-inclusive total.
- Amount
- $2,500
- Mode
- Add GST
- Rate
- 10%
GST is $250, and the GST-inclusive total the client pays is $2,750.
Quoting the GST-inclusive figure up front avoids awkward conversations later and makes the tax invoice match the agreed price exactly.
Who uses this tool
Tradespeople
Add GST to a labour and materials quote before sending it to a client.
Bookkeepers
Remove GST from inclusive supplier receipts to record the correct GST credit.
Online sellers
Check the GST component of a sale price when reconciling marketplace payouts.
Frequently asked questions
How do I calculate GST on a price in Australia?
Multiply a GST-exclusive amount by 0.1 to find the GST, or by 1.1 to find the GST-inclusive total. For a 200 dollar service, GST is 20 dollars and the total is 220 dollars. The calculator above does this automatically at the standard 10% rate.
How do I remove GST from a total that already includes it?
Divide the GST-inclusive total by 1.1 to find the original amount, then subtract that from the total to find the GST. A 330 dollar inclusive total becomes 300 dollars excluding GST and 30 dollars of GST. Dividing by 0.9 is a common mistake and gives the wrong figure.
Is GST always 10% in Australia?
The standard GST rate is 10% and has been since GST was introduced in 2000. Some items are GST-free, such as most basic food, certain health and education services, and some exports. The calculator lets you change the rate if you need to model a GST-free or partially taxable supply.
When does my business have to register for GST?
You must register once your annual turnover reaches 75,000 dollars, or 150,000 dollars for non-profits. Ride-share and taxi drivers must register from the first dollar. Below the threshold you can register voluntarily, which can help if you incur significant GST on purchases.
What is the difference between GST-free and input-taxed supplies?
GST-free supplies have no GST added and you can still claim GST credits on related purchases, for example most basic food and exports. Input-taxed supplies also have no GST added but you cannot claim credits on related costs, for example most financial services and residential rent.
Do I need to show GST separately on my invoices?
For tax invoices of 1,000 dollars or more you must show the GST amount or state clearly that the total includes GST, along with your ABN and the other required details. For sales under 1,000 dollars the requirements are lighter, but showing GST is still good practice.