Choose "Add GST" to turn an ex-GST price into a GST-inclusive total, or "Remove GST" to split a GST-inclusive amount into the price before GST and the GST itself. Australia’s GST rate is 10%, which is preset, but you can change the rate for other countries (for example 15% for New Zealand).
The maths is simple: adding GST is price × 1.10, and the GST inside a total is total ÷ 11. Amounts are rounded to the nearest cent. This is a general calculator, not tax advice. Check the ATO website or your accountant for how GST applies to your business.
Multiply the price by 1.10. For example, $100 plus GST is $110, of which $10 is GST.
Divide the GST-inclusive total by 11 to get the GST amount, then subtract it for the ex-GST price. A $110 total contains $10 GST.
Generally you must register for GST once your annual turnover reaches the ATO threshold ($75,000 at the time of writing). Check ato.gov.au for current rules.