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Reverse GST calculator

Find the GST inside a price that already includes it. Enter the price and see how much of it is GST and what it comes to before GST.

  • By Book Keeping Pros
  • Sources checked 15 Oct 2026

Take GST out of a price

Enter the price including GST. The result updates as you type.

In dollars and cents, such as 1,250.50

General information only. It works out the figures for the amount you enter and doesn't take your circumstances into account.

GST included

Enter an amount

Show working

Enter an amount to see the working.

How it works

GST is 10% of the value of a taxable sale.

Because GST is added on top of the value of a sale, the GST inside a GST-inclusive price is the price divided by 11. Taking a tenth of the price instead overstates the GST, a mistake the ATO warns about.

The calculator rounds that GST to the nearest cent and takes it away from the price, so the GST and the price before GST always add back up to the price you entered.

Worked example

The GST Act's own example is a car sold for $22,000, including GST. Dividing that price by 11 gives GST of $2,000, leaving a value of $20,000.

What the result assumes

  • The whole price is for one sale that is taxable at the standard rate.
  • The price you enter already includes GST. To add GST to an amount instead, use the GST calculator.
  • The GST is the price divided by 11, rounded to the nearest cent, as the ATO sets out for a tax invoice with one taxable sale.
  • It doesn't cover GST-free or input-taxed sales, or a price where only part of the sale is taxable.
  • It doesn't apply special valuation rules, such as the margin scheme, where the value of a sale isn't worked out from its price this way.

Sources

  1. A New Tax System (Goods and Services Tax) Act 1999

    Federal Register of Legislation. Compilation No. 96, compilation date 1 January 2026, released 30 January 2026. Checked 15 October 2026.

    Based on content from the Federal Register of Legislation at 15 October 2026. For the latest information on Australian Government legislation please go to https://www.legislation.gov.au. Licence: CC BY 4.0.

  2. How GST works

    Australian Taxation Office. Current at 14 September 2026, released 14 September 2026. Checked 14 October 2026.

    © Australian Taxation Office for the Commonwealth of Australia Licence: ATO website copyright notice (copy, adapt and distribute, without implying ATO endorsement).

  3. Calculating GST on purchases

    Australian Taxation Office. Current at 28 June 2024, released 28 June 2024. Checked 15 October 2026.

    © Australian Taxation Office for the Commonwealth of Australia Licence: Essentials copyright notice (copy, adapt and distribute, without implying ATO or Commonwealth endorsement).

  4. Tax invoices

    Australian Taxation Office. Current at 18 September 2026, released 18 September 2026. Checked 15 October 2026.

    © Australian Taxation Office for the Commonwealth of Australia Licence: ATO website copyright notice (copy, adapt and distribute, without implying ATO endorsement).

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Questions about this calculator

Something else on your mind? Ask us directly.

Why divide by 11 and not by 10?
GST is charged on the value of the sale, then added to it. So a GST-inclusive price is eleven parts, ten of value and one of GST, and the GST is one of those eleven parts. Dividing by 10 takes a tenth of the GST as well and gives too much.
Why don't the two figures always look like a round split?
The GST is rounded to the nearest cent first, and the price before GST is what's left of the price. That keeps the two figures adding up to the price you entered, even when the exact GST runs past the cent.
Can I use it on a receipt with several items?
No. This calculator works out one fully taxable sale at a time. The ATO allows different rounding methods for invoices with several taxable sales, so entering the receipt total can give a different GST amount even when every item is taxable.
What if I need to add GST instead?
Use the GST calculator. It starts from an amount before GST and shows the GST and the total including GST.

General information

This calculator applies the GST rule and rounding from the GST Act and ATO guidance to one GST-inclusive price. It's general information, not advice about your circumstances, so check that the whole sale is taxable before you use the figure. Sources checked 15 October 2026.