GST Calculator
The GST Calculator adds or removes Goods and Services Tax from any amount at the rate you choose. Enter a price and a GST rate to see the tax portion and the final price, or start from a tax-inclusive price to find the base amount and the GST hidden inside it.
Adding GST versus removing GST
There are two everyday GST calculations. Adding GST takes a base (exclusive) price and works out the tax to add on top. Removing GST takes a final (inclusive) price and works backwards to find the original amount and the tax already inside it. Getting these the right way round is where people usually slip up.
The formulas
To add GST: Tax = Amount × Rate ÷ 100, and Final = Amount + Tax. To remove GST from an inclusive price: Base = Inclusive ÷ (1 + Rate ÷ 100), and Tax = Inclusive − Base.
A worked example
A product costs 1,000 before tax at 18% GST. The tax is 180 and the final price is 1,180. Now reverse it: if the shelf price is 1,180 inclusive of 18% GST, the base is 1180 ÷ 1.18 = 1,000 and the GST inside it is 180. For intra-state sales that 180 typically splits into equal CGST and SGST of 90 each.
Common GST rates
Rates differ by country and product category, with several common slabs such as 5, 12, 18 and 28 percent in India. Always apply the rate that matches the specific goods or service, and remember that a price described as inclusive already contains the tax, so you must remove rather than add it.
How to use
- Enter your details in the fields above. The GST Calculator accepts everyday values and checks them as you type.
- Press the action button (or just start typing for live tools) to run the calculation.
- Read your result, along with any supporting figures, in the clearly labelled result box.
- Use Copy result to grab the answer, Reset to start again, or Copy link to share this tool.
Why use this tool
Finance Wave built the GST Calculator to be genuinely useful: it validates your input so you never see a broken result, formats numbers for your region automatically, and stays readable in both light and dark mode. Because everything happens on your device, it is private by design and keeps working even without an internet connection once the page has loaded.