GST Calculator

GST is one of those things that sounds simple until you're staring at an invoice wondering whether the price already includes it. If you've ever caught yourself doing shaky mental maths in front of a client, this calculator saves you from that little moment of panic.

A practical example: say you're a freelance designer quoting $1,850 ex GST for a logo package. Add 10% GST and the tax is $185, which makes the total $2,035 inc GST. Going the other way matters too. If a supplier gives you a bill for $330 inc GST, the GST portion is $30 and the GST-exclusive amount is $300. That's the number you actually want if you're checking margins, comparing quotes, or sorting your BAS records.

How to get the most out of this

Start by being clear on whether the number in front of you is GST-inclusive or GST-exclusive. That's where most mistakes happen. If you're quoting customers, use the "Add GST" option so your final total looks clean and professional. If you're reviewing receipts or invoices you've already paid, use "Remove GST" to see the real pre-tax cost. And if you're just trying to work out how much GST sits inside a total, the GST-only mode is the fastest path.

One small but important thing: don't just subtract 10% from a GST-inclusive amount. That gives the wrong answer. To remove GST properly, you divide by 1.1. It sounds minor, but on bigger numbers the gap gets annoying fast.

FAQs

Why can't I just take 10% off a GST-inclusive price?

Because GST is 10% of the original pre-tax amount, not 10% of the final total. A $110 total contains $10 GST, not $11.

Are all Australian purchases subject to GST?

Not quite. Basic food, many health services, education, and residential rent are common GST-free examples, while most goods and services still include it.

Should I round GST to the nearest cent?

Usually, yes. For everyday invoices and quotes, rounding to two decimal places keeps things tidy and lines up with how amounts are normally shown in Australia.