GST Exclusive Calculator

🇦🇺 Australian-built ✓ 10% GST rate (current) 🍺 No signup

If a price already has GST baked in, you do not lop off 10% to strip it out. You divide by 11. That single rule trips up more sole traders, tradies and small-business owners than almost anything else on a BAS, and the gap gets wider as the invoice gets bigger.

A GST exclusive calculator does the working for you – but only if you give it the right number to start with.

Why getting the exclusive figure right matters

GST in Australia is a flat 10%, set in 2000 and unchanged since. Once your turnover passes $75,000 (or $150,000 for non-profits), you must register, charge GST on taxable sales and report it on a quarterly BAS. Get the exclusive figure wrong by a few cents on every line, and the variance shows up at quarter-end – usually in your favour or the ATO’s, never neither.

We run a small consultancy out of a home office in inner-west Sydney, and we have seen how this lands in practice. A subbie sends through a $4,400 invoice ‘inclusive of GST’. The bookkeeper records $4,000 ex-GST and $400 GST. Add nine of those across a quarter and one dropped digit becomes a real reconciliation headache.

The maths is not hard. It is just specific.

Where ex-GST maths actually comes up

There are a few moments where this calculation matters most. The first is drafting a quote for a B2B client who only wants to see the base figures. The second is reconciling a supplier invoice that has buried the GST inside the line items. Then there is the BAS once a quarter, when every total needs to be split into its taxable and tax components. And there is always one customer at the counter who asks you the GST component on a $77 receipt while you are trying to lock up the shop.

What you’ll need

The price you want to convert, clearly marked as inclusive or exclusive
A basic calculator, or a GST exclusive calculator like the one on this site
A note of whether the item is taxable, GST-free or input-taxed (most things are taxable, but fresh fruit and vegies, basic groceries and most health and education are not)
Your invoice template or spreadsheet, so the figures drop straight in

Step-by-step: removing GST from any price

1. Confirm the price already includes GST

Before you touch the calculator, check the source document. A tax invoice in Australia must state either ‘GST included’ or show the GST as a separate line. If it says ‘plus GST’ or ‘ex GST’, the figure is already exclusive and there is nothing to strip.

If the page says nothing at all and the supplier is GST-registered, treat the figure as inclusive by default. The ATO’s display rules require the price shown to consumers to be the all-up figure, and most B2B quotes follow the same convention unless ‘plus GST’ is written next to the number.

2. Divide by 1.1 to get the GST-exclusive amount

This is the headline calculation. A GST-inclusive price is 110% of the base figure (100% goods plus 10% tax), so dividing by 1.1 gets you back to 100%.

Worked example: $550 ÷ 1.1 = $500 ex-GST.

Larger one: $13,750 ÷ 1.1 = $12,500 ex-GST.

And the awkward one: $99 ÷ 1.1 = $90 ex-GST.

If you punch the number into a GST exclusive calculator, this is the function it runs in the background.

3. Divide by 11 to find the GST component

Once you know the exclusive number, you can read the GST off it directly ($550 inc minus $500 ex equals $50 GST). The cleaner way is to divide the inclusive figure straight by 11.

Why 11? A GST-inclusive price is made up of 11 equal parts – 10 parts ex-GST plus one part GST. Divide by 11 and you isolate that one part.

$550 ÷ 11 = $50 GST.

$13,750 ÷ 11 = $1,250 GST.

$99 ÷ 11 = $9 GST.

This is also the figure that lands at 1A on your BAS as GST on sales – the inclusive total goes at G1.

4. Cross-check by going the other way

Take the exclusive figure and multiply by 1.1. If you do not land back on the inclusive number, something has gone sideways – usually a rounding error or a typo.

$500 × 1.1 = $550. Matches.

$90 × 1.1 = $99. Matches.

In a spreadsheet, run this as a separate column for at least the first month after rolling out a new template. It catches more mistakes than re-reading the formulas.

5. Record both figures on the invoice

The ATO accepts two formats on a tax invoice. Either show the GST as a separate line item (‘Subtotal $500, GST $50, Total $550’), or write ‘Total price includes GST’ below a single inclusive figure. Pick one and stick with it across every invoice you send – mixing formats inside the same client account is where messy reconciliations begin.

Common mistakes

Subtracting 10% from the inclusive price. $550 × 0.9 = $495, not $500. The error is small on a takeaway coffee and big on a $250,000 fitout, but it is wrong every time.
Quoting ‘plus GST’ to consumers in a retail setting. Under the Australian Consumer Law, a price tag that says ‘$100 + GST’ on a Bunnings-style shelf is a breach. The display rule requires the all-up figure for B2C sales. ‘Plus GST’ is fine in B2B quotes where both parties are registered.
Forgetting GST-free items. Fresh fruit and vegies, basic groceries, most health, education and certain childcare services are GST-free. Running a divide-by-11 over a Coles grocery run will give you a number, but not a useful one.
Mixing up the divisor. 1.1 strips GST off to get the exclusive figure. 11 isolates the GST component. We have seen people swap them on a Tuesday and not notice until the BAS draft is sitting on the screen on Friday.
Rounding too early. If a spreadsheet rounds each line to the nearest cent before summing, you can end up a few cents off the printed invoice total. Round at the end, not the beginning.
Treating a supplier’s mistake as your problem. If a supplier hands you an invoice that does not break out GST and is not marked ‘GST included’, you cannot claim a GST credit on it. Send it back.

Troubleshooting

If a calculator returns a number with three or more decimal places, round to two cents – the ATO accepts standard commercial rounding. If you are dealing with mixed supplies (some GST, some GST-free) on the same invoice, do the maths line by line, not on the total. And if you are unsure whether a supplier is GST-registered, run their ABN through the ABN Lookup tool – it is free and authoritative, and unregistered suppliers cannot charge you GST in the first place.

One last thing

If you quote ‘plus GST’ to a business client, write it next to every line on the page – not just the total. It looks fussy on the first read, but it removes any argument about which numbers are which when the invoice goes out six weeks later.

Frequently asked questions

What is a GST exclusive calculator?

A GST exclusive calculator strips the 10% goods and services tax out of a GST-inclusive price so you are left with the base amount. You enter the inclusive figure, the calculator divides it by 1.1, and it returns both the exclusive amount and the GST component. It is the reverse of an ‘add GST’ calculator, which multiplies a base price by 1.1.

How do I calculate the GST-exclusive price from a GST-inclusive amount?

Divide the inclusive price by 1.1. For example, $1,100 ÷ 1.1 = $1,000 ex-GST. To pull out the GST component on its own, divide the inclusive price by 11 ($1,100 ÷ 11 = $100 GST). Both calculations work for any inclusive figure as long as the supply is taxable.

Why divide by 1.1 instead of subtracting 10%?

Because the 10% was added to the base price, not the inclusive price. A $100 base item becomes $110 with GST – the $10 of GST is 10% of $100, but only about 9.09% of $110. Subtracting 10% from $110 gives you $99, which is wrong. Dividing $110 by 1.1 correctly returns $100.

What is the current GST rate in Australia?

GST in Australia is 10%. The rate has been unchanged since the tax was introduced on 1 July 2000, so the divide-by-1.1 and divide-by-11 shortcuts apply to every standard taxable supply.

When do I need to register for GST?

You must register once your annual GST turnover hits $75,000 ($150,000 for non-profits, and from the first dollar if you drive a taxi or rideshare). Below the threshold, registration is voluntary. Once registered, you charge GST on taxable sales, claim GST credits on business purchases and lodge a BAS.

Are all goods and services subject to GST?

No. Most basic foods, fresh fruit and vegetables, most health and medical care, most education courses and some childcare services are GST-free. Residential rent and most financial supplies are input-taxed. Running a GST exclusive calculation over a GST-free or input-taxed sale will return a number, but it is not a number you should put on a tax invoice.

What is the difference between GST inclusive and GST exclusive?

GST inclusive means the price you see already contains the 10% tax – it is the all-up figure a customer pays. GST exclusive means the price is the base amount before GST is added. Retail prices to consumers must be shown inclusive of GST under Australian Consumer Law, while B2B quotes are often written exclusive with ‘plus GST’ noted alongside.

Can I claim a GST credit if the supplier did not show GST on the invoice?

Generally no. To claim a GST credit, you need a valid tax invoice that either states ‘Total price includes GST’ or shows the GST as a separate line. If the supplier is registered and has charged GST without breaking it out, ask them to reissue the invoice. If they are not registered, no GST has been charged and there is nothing to claim.

The calculators and guides on gstcalculator.net.au are for general information only and do not constitute tax, financial, or legal advice. Consult a registered tax agent for advice specific to your situation.