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GST calculator

Add GST to a price, or work out how much GST is already inside a total. The number is calculated in cents, so adding GST and then removing it gives you exactly the figure you started with.

Work out the GST

Adding GST and removing GST are not the same sum

This trips people up constantly, and it is worth being precise about it.

Adding GST — multiply by 1.1. A $200 job becomes $220, and the GST is $20, which is 10% of the $200 price.
Removing GST — divide by 1.1. A $220 total is $200.00 of price plus $20.00 of GST. The GST is not 10% of the total; 10% of $220 is $22, which is wrong. The GST is one-eleventh of the total.

That is where the accountant's shortcut comes from: on a 10% GST-inclusive amount, divide by 11 to get the GST. Both routes give the same answer, and this calculator uses the division method so the parts always add back up to the total exactly.

Rounding, and why invoices can be a cent out

GST is calculated per sale, and each amount is rounded to the nearest cent. On an invoice with several lines, that means two accountants can legitimately reach totals one cent apart, depending on whether they rounded each line or the subtotal. The ATO accepts either. The invoice generator rounds per line and tells you when the alternative would have given a different result, so a one-cent difference on a supplier's invoice is explainable rather than alarming.

When GST does not apply

A 10% calculation is only right for a taxable sale. Two categories behave differently:

GST-free — most basic food, most medical and health services, education, going concerns. No GST is charged, but the sale still counts toward your GST turnover.
Input-taxed — residential rent, some financial supplies. No GST is charged and you generally cannot claim GST credits on related purchases.

If your invoice mixes taxable and non-taxable items, the invoice must clearly show which lines are taxable and the GST that applies to them. The invoice generator has a per-line GST toggle for exactly this.

Reference table

Common amounts, worked both ways.

GST reference table for common amounts
Price excl. GST	GST	Total incl. GST	Total incl. GST	GST inside	Price excl. GST

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Common questions

How do I add GST to a price?

Multiply the GST-exclusive price by 1.1, or work out 10% of it and add it on. A $100 job plus GST is $110: $100 of price plus $10 of GST. The calculator above does it in cents to keep the rounding honest.

How do I remove GST from a total?

Divide the GST-inclusive total by 1.1 to get the GST-exclusive amount. The GST is whatever is left over: on a $110 total that is $100.00 plus $10.00 GST. Dividing by 11 also gives the GST on a 10% inclusive amount.

Is the GST rate in Australia 10%?

Yes. GST has been 10% since it started on 1 July 2000 and that rate is set by the GST Act 1999. Some sales are GST-free (most basic food, many health services) or input-taxed (residential rent, some financial supplies), but the rate on taxable sales is 10%.

Why is my GST a cent different from my accounting software?

Because GST is calculated per line and rounded to the cent, a multi-line invoice can differ by a cent depending on whether GST is worked out line by line and added up, or worked out once on the subtotal. Both are accepted; this calculator shows you which one it used so a discrepancy is not a mystery.

Does a $100 cash job need GST?

Only if you are registered for GST. Registration is compulsory once your GST turnover reaches $75,000 ($150,000 for not-for-profits). Once registered, you charge GST on taxable sales regardless of how you are paid — cash included.