How to Calculate GST: Add and Remove GST With Examples
Knowing how to calculate GST comes down to two calculations: adding GST to a price, and taking it out of a total. Our GST calculator does both.
Adding GST
GST amount = price × rate ÷ 100. Total = price + GST amount.
Example at 18%: ₹1,000 × 18 ÷ 100 = ₹180, so the total is ₹1,180.
Removing GST
If a total already includes GST, divide it by (1 + rate). Pre-tax price = total ÷ 1.18 at 18%.
Example: ₹1,180 ÷ 1.18 = ₹1,000, and the GST inside it is ₹180. A common mistake is to subtract 18% of ₹1,180, which gives ₹967.60 and is wrong.
CGST, SGST and IGST
For a sale within one state, the GST is split equally into CGST and SGST. On ₹180 of GST that is ₹90 each. For a sale between states, the full ₹180 is charged as IGST.
Which rate to use
The rate depends on the product or service, and the GST Council can change it. Always confirm the current rate on the official GST portal or with your accountant before you issue an invoice.
