Add GST, or find the GST hiding inside a total.
A free GST calculator from InvoiceSonic, Australian invoicing software for tradies and sole traders. Australian GST is 10%. Adding it is easy; taking it back out of a GST-inclusive figure is where people go wrong — you divide by 11, not by 10. Enter any amount below to get the ex-GST price, the GST component and the inclusive total.
The reverse calculation is where most errors happen. GST was added at 10%, but it is one eleventh of the final figure — taking 10% off a $110 total gives $99, which is wrong.
| Price ex GST | GST (10%) | Total inc GST |
|---|---|---|
| 10.00 | 1.00 | 11.00 |
| 50.00 | 5.00 | 55.00 |
| 100.00 | 10.00 | 110.00 |
| 250.00 | 25.00 | 275.00 |
| 500.00 | 50.00 | 550.00 |
| 1,000.00 | 100.00 | 1,100.00 |
| 2,500.00 | 250.00 | 2,750.00 |
| 5,000.00 | 500.00 | 5,500.00 |
Registration is compulsory once GST turnover reaches 75,000 in a 12-month period.
To add GST, multiply the price by 1.1 — $100 becomes $110. To find the GST inside a GST-inclusive price, divide by 11 — a $110 total contains $10 of GST. To get the ex-GST price from an inclusive one, divide by 1.1.
Divide the GST-inclusive total by 11 to get the GST component. This catches people out because 10% was added but the GST is only one eleventh of the final figure — not 10% of it. Taking 10% off a $110 total gives $99, which is wrong; the correct ex-GST price is $100.
10% on most goods and services. Some supplies are GST-free, including most basic food, most medical and health services, most education courses, and exports. Input-taxed supplies such as residential rent and most financial services also carry no GST.
Once your GST turnover reaches $75,000 in a 12-month period, or if you provide taxi or rideshare services regardless of turnover. Non-profits register at $150,000. Below the threshold registration is optional — but if you are not registered you must not charge GST, and you cannot issue a tax invoice. Thresholds change; confirm the current figure at ato.gov.au before you register.
If you are registered for GST and the sale is over $82.50 including GST, the buyer can ask for a tax invoice, which must show your ABN, the date, a description of what was supplied, and either the GST amount or a statement that the total includes GST. Under $1,000 the requirements are lighter than over $1,000, which must also show the buyer's identity or ABN. General information only — check ato.gov.au for the current requirements.
The rate and the rules differ. New Zealand GST is 15%, so you multiply by 1.15 and divide an inclusive total by 7.667. India uses multiple GST slabs (5%, 12%, 18%, 28%) depending on the goods or service. This calculator uses the Australian 10% rate.
ABN invoice template · Invoice generator Australia · Markup calculator (AU) · Quote template Australia · Progress claim template (AU) · Free invoice generator
General information only, current at August 2026, and not tax advice. Check ato.gov.au or your accountant for your situation.