GST / VAT Calculator
Add tax to a price, or work backwards from a tax-inclusive total to find the net amount. Preset rates cover the most common jurisdictions.
| Net (excluding tax) | — |
| Tax amount | — |
| Gross (including tax) | — |
How to use the GST / VAT Calculator
- Choose whether you are adding tax to a net price or extracting it from a tax-inclusive total.
- Enter the amount and the rate, or tap one of the common rate chips.
- Press Calculate to see the net, tax and gross figures with the working.
Adding versus removing tax
Adding is straightforward: multiply the net by the rate and add it on. Removing is where mistakes happen, because subtracting the rate from the gross gives the wrong answer.
At 20%, a gross price of 120 has a net of 100 — but 120 minus 20% is 96. The correct operation is division: net = gross ÷ (1 + rate ÷ 100). The tax fraction shortcut follows from this: at 20% the tax is one sixth of the gross, at 10% it is one eleventh, and at 5% it is one twenty-first.
GST, VAT and sales tax are not the same thing
GST and VAT work the same way mechanically — tax is charged at each stage of the supply chain, and registered businesses reclaim what they paid on inputs, so the net burden falls on the final consumer. The names are regional: GST in Australia, New Zealand, Canada, India and Singapore; VAT across the UK and EU.
US sales tax is structurally different. It is charged once at the final sale, and the rate is set by state, county and city combined — so a single street can span two rates. Because of this, US prices are almost always displayed before tax, while GST and VAT jurisdictions require consumer prices to be shown tax-inclusive.
Rates vary by product
Most systems have more than one rate. The UK charges 20% standard, 5% on domestic fuel and 0% on most food and children's clothing. India's GST runs in slabs from 0% to 28% depending on the item. Canada layers a federal GST with provincial taxes that may be combined into a single HST or charged separately.
Enter the rate that applies to your specific goods rather than the headline national rate, and check current rates with the tax authority before relying on a figure for filing.
Frequently asked questions
How do I find the tax inside a price?
Switch to "Remove tax from gross price" and enter the total. The tool divides by 1 plus the rate to recover the net, then reports the difference as tax.
Why is my figure a cent off my invoice?
Accounting systems differ in where they round — per line item, per tax rate, or on the invoice total. Over many lines these choices diverge by a cent or two. Follow your jurisdiction's rounding rule for filings.
Can I use this for US sales tax?
Yes, if you know your combined rate. Because state, county and city rates stack, look up the exact rate for the delivery address rather than using a state average.
Does it handle multiple rates on one invoice?
Not in a single calculation. Group your line items by rate and run each group separately, then add the tax amounts together.
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