GST, VAT and Sales Tax: Adding and Removing Tax Correctly
Whether it's called GST, VAT or sales tax, the idea is the same: a percentage is added to the price of goods and services. Businesses need to add it to invoices, and both businesses and buyers often need to work out how much tax is hidden inside a price that already includes it. The free GST calculator on this page gives you the answer in seconds.
How to take GST out of a total (extract GST from the total amount)
When a price already includes GST, you can't just take 18% (or 10%) of it, because the percentage applies to the price before tax. Use these formulas instead:
Amount excluding GST = Total ÷ (1 + Rate ÷ 100)
| GST rate | Shortcut to find the GST in a total | Example |
|---|---|---|
| 5% | Total ÷ 21 | GST in 1,050 = 50 |
| 9% | Total × 9 ÷ 109 | GST in 1,090 = 90 |
| 10% | Total ÷ 11 | GST in 110 = 10 |
| 15% | Total × 3 ÷ 23 | GST in 115 = 15 |
| 18% | Total × 18 ÷ 118 | GST in 1,180 = 180 |
| 20% | Total ÷ 6 | VAT in 120 = 20 |
Common mistake: taking 10% of a total does not give the GST. 10% of 1,100 is 110, but the GST included in 1,100 at 10% is only 100, because 1,000 + 10% = 1,100. Select "Extract GST from total" in the calculator above to do this instantly for any amount and rate.
How to add GST to an amount (for example, 150 plus GST)
If you know the price before tax, multiply it by the rate to get the tax, then add the two together:
Tax = Net price × Rate ÷ 100 and Gross price = Net price + Tax.
For example, 1,000 at 18% gives a tax of 180 and a total of 1,180. Here is what 150 plus GST comes to at common rates:
| Rate | GST on 150 | 150 plus GST |
|---|---|---|
| 5% | 7.50 | 157.50 |
| 9% | 13.50 | 163.50 |
| 10% | 15.00 | 165.00 |
| 15% | 22.50 | 172.50 |
| 18% | 27.00 | 177.00 |
The same works for any "plus tax" price. For example, 359 plus tax is 376.95 at 5%, 394.90 at 10% and 423.62 at 18%. Choose "Add GST to amount" above and tap a quick rate to see it instantly.
Why you can't just subtract the percentage
This is where many people go wrong. To find the net price from a tax-inclusive price, you can't simply subtract 18%. Instead, divide by (1 + rate):
Net price = Gross price ÷ (1 + Rate ÷ 100).
So 1,180 including 18% tax has a net price of 1,000, not 967.60. Select "Remove tax" in the calculator to do this automatically.
GST and VAT rates in popular countries
| Country | Tax | Standard rate |
|---|---|---|
| India | GST | 5% and 18% main slabs, 40% on some luxury and sin goods |
| Australia | GST | 10% |
| New Zealand | GST | 15% |
| Singapore | GST | 9% |
| Canada | GST | 5% federal (HST or provincial tax may apply) |
| United Kingdom | VAT | 20% |
| UAE | VAT | 5% |
| Pakistan | Sales tax | 18% |
Rates can change and many countries have reduced or zero rates for certain goods, so always check the latest rate with your tax authority.
Split tax between two authorities
In some systems, tax on a sale is divided between two authorities. In India, for example, intra-state sales split GST equally into CGST and SGST. The calculator shows this equal split for convenience.
Tips for small businesses
- Check the correct rate for each product or service; rates often vary by category.
- Show the net amount, tax and total clearly on every invoice.
- Keep records of tax you pay on purchases, as many systems let you claim it back as input credit.
- Confirm registration thresholds and filing deadlines with your tax authority.
Planning further? You may also find our Income Tax Calculator, Salary Calculator useful, or explore all calculators.
Further reading: Goods and Services Tax, India (Wikipedia) · GST rate of 9% (IRAS Singapore)