Australian GST Calculator
Add GST to a price or find the GST already included in a total. Choose the supported supply category and keep net price, GST and the amount payable clearly separated.
Calculation breakdown
How to use this tool
- Choose GST-inclusive or exclusive input.
- Enter the amount and confirm the supply category.
- Review the net price, tax and gross total.
How the result is calculated
For a standard 10% taxable supply, GST is 10% of the price before tax. Within a GST-inclusive total, the GST component is one-eleventh of that total.
Worked example
A $100 price before GST becomes $110. Working backwards from $110, the GST component is $10 and the price before tax is $100.
What this result does not cover
The calculator does not decide whether a supply is taxable, GST-free or input taxed. Registration and input-tax-credit questions need separate checks.
Questions people ask
Why is GST not 10% of the inclusive total?
Because the total already contains the tax; use the inclusive fraction.
Are GST-free and input taxed identical?
No. Their treatment can differ beyond the customer's tax amount.
Does this create a compliant tax invoice?
No. It provides calculations; invoice requirements are separate.
Supported scope and official sources
10% standard GST arithmetic with explicit taxable, GST-free and input-taxed categories. Optional mixed lines replace the single amount. Half-up cent rounding; this is not a tax invoice or a classification decision.
Source snapshot: 22 October 2026. Independent specialist review is pending. Calculations do not confirm eligibility or replace official decisions.