GST Calculator
Add or remove Australia's 10% GST from a price.
- GST component
- $100
This calculator provides estimates only. It is general information, not financial or taxation advice, and doesn't account for your full personal circumstances. Confirm figures with your lender or a licensed adviser before making a decision.
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How this calculator works
Goods and Services Tax (GST) is a flat 10% tax added to most goods and services sold in Australia, set under the A New Tax System (Goods and Services Tax) Act 1999 and unchanged since it was introduced in 2000. This calculator adds GST to a GST-exclusive amount, or extracts the GST component from a GST-inclusive amount.
Choose "Add GST" if your amount doesn't yet include GST (common when working from a supplier's ex-GST price), or "Remove GST" if your amount already includes it (common when working backward from a customer-facing price) and enter the amount.
Worked example: adding GST to a $1,000 ex-GST amount gives $100 GST and a $1,100 GST-inclusive total. Going the other way, removing GST from a $1,100 GST-inclusive amount gives back the same $100 GST and a $1,000 ex-GST amount — the two directions are exact inverses of each other.
A common mistake is dividing a GST-inclusive amount by 1.1 incorrectly or multiplying by 10% instead of dividing by 11 — the GST component of a GST-inclusive amount is always inclusive amount ÷ 11, not inclusive amount × 10%, since the 10% applies to the exclusive amount, not the inclusive one.
Frequently asked questions
- Why isn't the GST component of an inclusive amount just 10% of that amount?
- Because the 10% rate applies to the GST-exclusive amount, not the inclusive one. For a GST-inclusive price, the GST component is exactly one-eleventh of the total (inclusive amount ÷ 11), not 10% of the inclusive total.
- Does every business need to charge GST?
- Only businesses registered for GST — generally required once turnover exceeds $75,000 a year (or $150,000 for non-profits) — need to charge it, though businesses under that threshold can register voluntarily.
- Are all goods and services subject to GST?
- No — some items are GST-free (most basic food, many medical and educational services) or input-taxed (like residential rent and financial services). This calculator assumes the standard 10% rate applies; check ATO guidance for GST-free or input-taxed categories.