🧾 GST Calculator
By ToolNimba Finance Team · Reviewed by ToolNimba Editorial Review, tax and finance content · Updated 2026-06-19
This calculator is for general estimates only and is not tax advice. GST rates, rounding rules and the items that are taxable, zero-rated or exempt differ by country and change over time. Always confirm the current rate and rules with your local tax authority or a qualified accountant before relying on a figure for an invoice or a tax return.
GST (Goods and Services Tax) is a consumption tax added to the price of most goods and services. This calculator works both ways: enter a net amount to add GST and see the tax and gross total, or enter a GST-inclusive total to remove GST and find the original net price. Set your own rate (the default is 10%), and the net, GST, and total update instantly so you can build or check an invoice in seconds.
What is the GST Calculator?
GST is a value-added tax charged as a percentage of a sale price. The maths is simple but it runs in two directions, which is where people get caught out. To add GST to a net (GST-exclusive) amount you multiply by the rate: GST = amount x rate / 100, and the gross total = amount + GST. At a 10% rate, a $100 net price carries $10 of GST and a $110 total.
The harder direction is removing GST from a price that already includes it. You cannot simply take 10% off a GST-inclusive total, because the 10% was charged on the smaller net figure, not on the gross. Instead you divide by (1 + rate / 100). At 10%, a $110 inclusive total divides by 1.10 to give a $100 net price, leaving $10 of GST. Taking a flat 10% off $110 would wrongly give $99, so the divide-back method matters whenever you need to separate the tax from a shelf price or a receipt.
GST is known by different names and rates around the world: it is GST in Australia, New Zealand, India, Canada and Singapore, and VAT in the UK, the European Union and many other countries, but the add and remove arithmetic is identical. The rate is the only thing you change. Because GST is ultimately paid by the final consumer, registered businesses generally collect it on sales and reclaim it on purchases, so working cleanly between net, GST and gross figures is a routine part of invoicing and bookkeeping.
When to use it
- Adding GST to a quote or invoice so the customer sees the net price, the GST, and the total they will pay.
- Removing GST from a GST-inclusive shelf price or receipt to find the net amount for your bookkeeping.
- Checking that the GST line on a supplier invoice has been calculated correctly.
- Comparing a GST-exclusive quote with a GST-inclusive one so you are comparing like with like.
How to use the GST Calculator
- Choose a mode: Add GST to work from a net price, or Remove GST to work back from a GST-inclusive total.
- Enter the amount (the net price in Add mode, or the gross total in Remove mode).
- Enter the GST rate, or tap one of the quick-rate buttons. The default is 10%.
- Read off the net amount, the GST amount, and the total with GST.
Formula & method
Worked examples
Add 10% GST to a net price of $200.
- GST = 200 x 10 / 100 = $20.00
- total = 200 + 20 = $220.00
Result: Net $200.00, GST $20.00, total $220.00
Remove 10% GST from a GST-inclusive total of $550.
- net = 550 / (1 + 10 / 100) = 550 / 1.10 = $500.00
- GST = 550 - 500 = $50.00
Result: Net $500.00, GST $50.00, total $550.00
Add 15% GST to a net price of $80.
- GST = 80 x 15 / 100 = $12.00
- total = 80 + 12 = $92.00
Result: Net $80.00, GST $12.00, total $92.00
Adding GST at 10% to common net amounts
| Net amount | GST (10%) | Total with GST |
|---|---|---|
| $50.00 | $5.00 | $55.00 |
| $100.00 | $10.00 | $110.00 |
| $250.00 | $25.00 | $275.00 |
| $1,000.00 | $100.00 | $1,100.00 |
GST and VAT standard rates in selected countries (check current rates before use)
| Country | Tax name | Standard rate |
|---|---|---|
| Australia | GST | 10% |
| New Zealand | GST | 15% |
| India | GST | 5% to 28% by slab |
| Singapore | GST | 9% |
| United Kingdom | VAT | 20% |
Common mistakes to avoid
- Subtracting the rate to remove GST. Taking 10% off a $110 GST-inclusive total gives $99, which is wrong. The 10% was charged on the $100 net price, not on the $110 gross, so you must divide by 1.10 to get $100 back.
- Mixing inclusive and exclusive prices. Comparing a GST-exclusive quote against a GST-inclusive one makes the inclusive one look dearer than it is. Put both on the same basis (net or gross) before you compare.
- Using the wrong rate. GST and VAT rates differ by country and some items are zero-rated or exempt. Using the default rate for a country with a different rate, or for an exempt item, will overstate or understate the tax.
- Ignoring rounding rules. Tax authorities have specific rounding rules for invoices, often to the nearest cent per line or per invoice. Small rounding differences are normal, so match the convention your jurisdiction requires.
Glossary
- GST
- Goods and Services Tax, a consumption tax added as a percentage of the price of most goods and services.
- VAT
- Value Added Tax, the name used for the same kind of consumption tax in the UK, the EU and many other countries.
- Net (GST-exclusive)
- The price before GST is added.
- Gross (GST-inclusive)
- The price after GST has been added, which is what the customer actually pays.
- Input tax credit
- GST a registered business has paid on its purchases, which it can usually reclaim against the GST it collects on sales.
Frequently asked questions
How do I add GST to a price?
Multiply the net price by the GST rate and divide by 100 to get the GST, then add it to the net price for the total. At 10%, a $100 net price gives $10 GST and a $110 total. The Add GST mode does this for you.
How do I remove GST from a GST-inclusive price?
Divide the GST-inclusive total by (1 + rate / 100). At 10% you divide by 1.10, so a $110 inclusive total becomes a $100 net price with $10 of GST. Use the Remove GST mode for this.
Why can I not just subtract 10% to remove GST?
Because the 10% was charged on the smaller net amount, not on the larger gross total. Subtracting 10% from $110 gives $99, but the correct net price is $100. You must divide by 1.10 instead of subtracting 10%.
What GST rate should I use?
Use the standard rate for your country, for example 10% in Australia, 15% in New Zealand or 9% in Singapore, unless the item is zero-rated or exempt. Rates change over time, so confirm the current rate with your tax authority.
Is GST the same as VAT?
They are essentially the same kind of consumption tax under different names. GST is used in Australia, New Zealand, India, Canada and Singapore, while VAT is used in the UK, the EU and elsewhere. The add and remove calculations are identical.
Does this calculator store my figures or send them anywhere?
No. Everything runs in your browser, so your amounts never leave your device and nothing is sent to a server. Refreshing the page clears the inputs.
Sources
- GST for business , Australian Taxation Office
- How VAT works , UK Government (GOV.UK)