GST & Sales Tax Calculator
Add or remove Australian GST (10%), or work out US sales tax for any state — with the working shown.
How Australian GST works
The Goods and Services Tax (GST) is a flat 10% tax on most goods and services sold in Australia. Prices shown to consumers must include GST, which leads to the two calculations everyone needs:
- Adding GST (you have the base price): multiply by 1.1. A $200 service becomes $220 including $20 GST.
- Removing GST (you have the total): divide the total by 11 to find the GST. A $220 invoice includes $20 GST — the base price is $200.
The divide-by-11 trick works because a GST-inclusive price is 110% of the base, so exactly one eleventh of it is tax. Businesses registered for GST (required once turnover reaches $75,000) collect GST on sales and claim credits for GST paid on purchases, reporting the difference to the ATO on a Business Activity Statement (BAS).
Some items are GST-free: most fresh food, most medical and health services, most education courses, and exports. When in doubt, check the ATO website.
How US sales tax works
The United States has no national sales tax. Each state sets its own rate — from 0% in Delaware, Montana, New Hampshire and Oregon up to 7.25% in California — and in most states, cities and counties add local tax on top. That's why the checkout total in Chicago (over 10% combined) differs from one in Portland (0%). Unlike GST, US shelf prices are almost always shown before tax, which surprises many Australian visitors.
| State | Base state rate | State | Base state rate |
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Base state rates only — many cities and counties add local tax on top, and rates change. Use the local-rate field above for your combined rate, and verify important figures with your state's revenue department.
Frequently asked questions
How do I calculate GST in Australia?
To add GST, multiply the price by 1.1. To find the GST inside a total, divide by 11. A $110 total includes $10 GST on a $100 base.
Why divide by 11 to remove GST?
A GST-inclusive price is 110% of the base price, so the tax is 10/110 — exactly one eleventh — of the total.
Which US states have no sales tax?
Delaware, Montana, New Hampshire and Oregon have no state sales tax. Alaska has no state rate but allows local sales taxes.
Is this calculator exact?
The GST calculation is exact. For US sales tax, the state base rates are accurate but local surcharges vary block by block — enter your local rate for a combined figure, and confirm important amounts with an official source.