How to add GST
To add GST to a base price, multiply the base amount by the GST rate divided by 100, then add that to the base amount. For example, adding 18% GST to ₹1,000 gives ₹180 in GST, for a final amount of ₹1,180.
How to remove GST from an inclusive price
If a price already includes GST and you need to find the base amount, divide the total by (1 + GST rate ÷ 100). For a GST-inclusive price of ₹1,180 at 18%, the base price is ₹1,180 ÷ 1.18 = ₹1,000.
Common GST slabs in India
India uses four main GST slabs — 5%, 12%, 18%, and 28% — applied depending on the category of goods or services. This calculator includes all four as quick presets, plus a custom rate field for anything else.