GST Explained: How to Calculate GST on Any Amount

Goods and Services Tax (GST) is a single indirect tax applied to the supply of goods and services in India, replacing a patchwork of older taxes. Common GST slabs are 5%, 12%, 18%, and 28%, depending on the category of goods or services.

Adding GST to a Price

If a product costs ₹1,000 before tax and attracts 18% GST:

GST amount = 1,000 × 18 / 100 = ₹180
Total price = ₹1,000 + ₹180 = ₹1,180

Extracting GST from an Inclusive Price

Sometimes the price you see already includes GST, and you need to work out the base price and tax component separately. If a GST-inclusive price is ₹1,180 at 18% GST:

Base price = 1,180 / (1 + 18/100) = ₹1,000
GST amount = ₹1,180 − ₹1,000 = ₹180

CGST and SGST

For sales within the same state, GST is typically split equally into CGST (Central GST) and SGST (State GST) — so an 18% GST amount of ₹180 would be ₹90 CGST plus ₹90 SGST. For inter-state sales, the full amount is charged as IGST instead.

Our GST calculator below handles both directions — adding GST to a base price, or extracting it from an inclusive price — along with the CGST/SGST split.