Tool

GST Calculator Australia: Add or Remove GST (Reverse GST)

Free Australian GST calculator. Remove GST from a total (reverse GST) or add 10% GST to a price in one step, with the formulas and a quick-reference table.

Add or remove GST

Amount ($)

Remove GST: $110.00 includes GST

$100.00 ex-GST amount

$10.00 GST included (total ÷ 11)

Add GST: $110.00 excludes GST

$121.00 GST-inclusive price

$11.00 GST to add (amount × 10%)

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How to calculate GST in Australia

GST in Australia is 10% of the price before GST. To add GST, multiply the price by 1.1. To remove GST from a total that already includes it (reverse GST), divide the total by 1.1. The GST inside a GST-inclusive total is always the total divided by 11.

Removing GST (reverse GST)

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

Example: a $220 receipt includes $20 of GST ($220 ÷ 11) and is $200 before GST ($220 ÷ 1.1).

Adding GST

GST to add = Ex-GST price × 0.1
GST-inclusive price = Ex-GST price × 1.1

Example: a $200 ex-GST price attracts $20 of GST, so you charge $220.

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

The most common mistake: taking 10% off the total

10% of a $110 total is $11, but the GST in $110 is only $10. Because GST is added on top of the price, it makes up one-eleventh (about 9.09%) of a GST-inclusive total, not 10%. The error grows with the amount: taking 10% off an $11,000 invoice overstates the GST by $100.

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

If you’re reverse-calculating GST from a pile of receipts every quarter, that’s the part Budgetly automates: each card transaction is coded with its GST as it happens and matched to its receipt.

GST quick-reference table

Common amounts, worked both ways at 10% GST.

Amount	Remove GST: ex-GST amount	GST included	Add GST: GST-inclusive price	GST added
$1.00	$0.91	$0.09	$1.10	$0.10
$10.00	$9.09	$0.91	$11.00	$1.00
$50.00	$45.45	$4.55	$55.00	$5.00
$100.00	$90.91	$9.09	$110.00	$10.00
$110.00	$100.00	$10.00	$121.00	$11.00
$150.00	$136.36	$13.64	$165.00	$15.00
$200.00	$181.82	$18.18	$220.00	$20.00
$500.00	$454.55	$45.45	$550.00	$50.00
$1,000.00	$909.09	$90.91	$1,100.00	$100.00
$5,000.00	$4,545.45	$454.55	$5,500.00	$500.00
$10,000.00	$9,090.91	$909.09	$11,000.00	$1,000.00

When to add GST

Add GST when you’re pricing a taxable sale or writing a quote or invoice. If your business is registered for GST, the price you charge customers generally needs to include it, and you report the GST you collect on your BAS.

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.

Who needs to register for GST?

Entity type	Must register when GST turnover (current or projected) is
Business	$75,000 or more
Non-profit organisation	$150,000 or more
Taxi, limousine and ride-sourcing drivers	Any turnover
Businesses claiming fuel tax credits	Any turnover

Businesses below the threshold can register voluntarily to claim GST credits on purchases. See the ATO’s GST registration guidance for the full rules.

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.

How do I add GST to a price?

Multiply the ex-GST amount by 1.1. For example, $100 ex-GST becomes $100 × 1.1 = $110 inc. GST. The GST component is $10 (10% of the original price).

Is GST 10% of the total price?

No. GST is 10% of the price before GST, which works out to one-eleventh (about 9.09%) of a GST-inclusive total. Taking 10% off a $110 total gives $11, but the GST in $110 is only $10. Always divide a GST-inclusive total by 11 to find the GST.

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.

What is the difference between GST-inclusive and GST-exclusive pricing?

GST-inclusive pricing includes the 10% tax in the displayed price. GST-exclusive pricing shows the base price before tax. In Australia, consumer-facing prices are generally displayed GST-inclusive, while B2B pricing is often quoted ex-GST.

Do all Australian businesses need to charge GST?

Businesses with a GST turnover (current or projected) of $75,000 or more (or $150,000 for non-profit organisations) must register for GST and charge it on taxable supplies. Businesses below this threshold can choose to register voluntarily. Taxi, limousine and ride-sourcing drivers, and businesses that want to claim fuel tax credits, must register regardless of turnover.

Is GST included in the price on Australian receipts?

Usually, yes. Prices shown to customers in Australia generally include GST. A valid tax invoice either shows the GST amount as a separate line or states that the total price includes GST, in which case the GST is one-eleventh of the total. To claim a GST credit on a purchase over $82.50 (including GST) you need a valid tax invoice. See our guide to tax invoice requirements in Australia for what it must include.

Methodology and disclaimer

This calculator uses the standard Australian GST rate of 10%, which has applied since GST started on 1 July 2000, as published by the Australian Taxation Office (ATO). Removing GST divides a GST-inclusive amount by 11 to find the GST component and by 1.1 to find the ex-GST amount. Adding GST multiplies a GST-exclusive amount by 0.1 for the GST and by 1.1 for the total. Results are rounded to the nearest cent so the GST and ex-GST amounts always add back to the total.

This tool provides estimates only and does not constitute financial, tax, or legal advice. It does not account for GST-free items, input-taxed supplies, or special rules for specific industries. Always consult a registered tax agent or BAS agent for your specific circumstances. Rate checked 9 October 2026.

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