Tool

Reverse GST Calculator

Free reverse GST calculator for Australian businesses. Enter a GST-inclusive amount to instantly see the GST component and ex-GST price.

How the reverse GST formula works

The Australian GST rate is 10%. When you have a GST-inclusive amount and need to work backwards:

  • GST component = Total ÷ 11
  • Ex-GST amount = Total ÷ 1.1

This works because the GST-inclusive price is 110% of the original price (100% + 10% GST). Dividing by 11 isolates the one-eleventh that represents the tax.

When to use a reverse GST calculator

Reverse GST calculations are common when:

  • Processing employee expense receipts that show only the total amount
  • Reconciling credit card statements where GST is not itemised
  • Preparing your quarterly BAS and claiming input tax credits
  • Checking supplier invoices for correct GST treatment

GST-free items to watch for

Not everything attracts GST. Common GST-free categories include:

  • Most basic food (fresh fruit, vegetables, bread, meat, dairy)
  • Some education courses
  • Some medical, health, and care services
  • Exports of goods and services
  • Sales of going concerns

If an item is GST-free, the “inclusive” amount already has no GST component, so reverse calculating would give an incorrect result.

Enter the GST-inclusive amount

$9.09 GST component
$90.91 ex-GST amount
10% GST rate

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This calculator provides estimates only and is not financial or tax advice. For accurate figures tailored to your business, work with a registered tax agent or accountant. Rates current as at 1 July 2025.

GST at the standard Australian rate of 10%. Methodology

Frequently asked questions

How do you reverse calculate GST in Australia?

To find the GST component of a GST-inclusive price, divide the total by 11. To find the ex-GST amount, divide by 1.1. For example, if the total is $110, the GST is $110 ÷ 11 = $10, and the ex-GST amount is $110 ÷ 1.1 = $100.

What is the GST rate in Australia?

The Goods and Services Tax (GST) rate in Australia is 10%. It applies to most goods, services, and other items sold or consumed in Australia. Some items are GST-free, including basic food, certain medical services, and some educational courses.

When would I need to reverse calculate GST?

You need to reverse calculate GST when you have a receipt or invoice showing the total (GST-inclusive) amount and need to determine the GST component for your BAS reporting, expense categorisation, or input tax credit claims.

Is GST included in the price on Australian receipts?

Australian businesses registered for GST must issue tax invoices that show the GST amount separately for sales over $82.50 (inc. GST). For sales of $82.50 or less, the total price can be shown as GST-inclusive without a separate GST line.

Methodology and disclaimer

This calculator uses the standard Australian GST rate of 10% as set by the Australian Taxation Office (ATO). The formula divides the GST-inclusive amount by 11 to find the GST component, and by 1.1 to find the ex-GST amount.

This tool provides estimates only and does not constitute financial, tax, or legal advice. Results may not account for GST-free or input-taxed supplies. Always consult a registered tax agent or BAS agent for your specific circumstances. Rates are current as at 1 July 2025.

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