GST Calculator (Australia & NZ)

Add GST to a price or remove GST from a GST-inclusive price. Defaults to Australia’s 10% (one-eleventh); use 15% for New Zealand.

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Rates as of 2026: Australia 10%, New Zealand 15%. Other GST countries differ (e.g. Canada’s federal GST is 5%, Singapore 9%) and rates can change, so check your tax authority. Your rate is remembered on this device.
Your rate is remembered on this device.
Price including GST
$110.00
GST
$10.00
Price excluding GST
$100.00

Estimate generated with SortedSums: https://sortedsums.com/gst-calculator/. For informational purposes only; verify before relying on it.

Estimate only. This tool is for informational and educational purposes. Results depend on your inputs and simplifying assumptions, and are not a substitute for professional engineering, design or financial advice. Always verify with a qualified professional and applicable codes before purchasing, building or making decisions.

How it’s calculated

To add GST, multiply the GST-exclusive price by the rate. To find the GST inside a GST-inclusive price, use the fraction rate ÷ (100 + rate). In Australia (10%) that is one-eleventh of the price; in New Zealand (15%) it is 3/23.

GST = exclusive price × rate Inclusive price = exclusive price × (1 + rate) GST in an inclusive price = inclusive × rate ÷ (100 + rate) Australia: inclusive ÷ 11 New Zealand: inclusive × 3 ÷ 23

Example (ATO): a ride-sourcing fare of $55 including GST contains $55 ÷ 11 = $5 GST, so the fare excluding GST is $50. Example (IRD): $100 including NZ GST contains 3/23 × $100 = $13.04 GST.

Whether GST applies depends on registration and the type of supply (some are GST-free or input-taxed). Check the ATO or IRD guidance or a registered tax agent.

Frequently asked questions

Why divide by 11 and not take off 10%?

The 10% is charged on the exclusive price, so GST is 10 parts out of 110 in the inclusive price, which is 1/11. Taking 10% off $110 gives $99, which is wrong; $110 ÷ 11 = $10 GST and $100 net.

How do I remove 15% NZ GST?

Multiply the GST-inclusive price by 3/23 to get the GST, or divide the price by 1.15 to get the GST-exclusive amount. $230 inclusive → $30 GST, $200 exclusive.

Do I have to show GST on a tax invoice?

In Australia a tax invoice must show the GST amount, or state "Total price includes GST" when GST is exactly one-eleventh of the total. See the ATO tax invoice rules.

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Sources

Formulas are taken from the free public references above. Results are provided “as is” for informational and educational purposes only. See our disclaimer.

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