How to use the GST calculator
- Enter the amount in rupees.
- Pick a GST rate or type any rate in the box.
- Choose whether your amount excludes GST (you want to add tax on top) or includes GST (you want to find the price before tax).
- Choose Same state to split the tax into CGST and SGST, or Other state to show IGST.
GST formulas with examples
Adding GST
GST = Amount × Rate ÷ 100 and Total = Amount + GST.
Example: a service costs ₹1,000 before tax at 18%. GST = 1,000 × 18 ÷ 100 = ₹180, so the customer pays ₹1,180. Within the same state this is split into ₹90 CGST and ₹90 SGST.
Removing GST
Price before GST = Total × 100 ÷ (100 + Rate) and GST = Total − Price before GST.
Example: you paid ₹1,180 including 18% GST. Price before GST = 1,180 × 100 ÷ 118 = ₹1,000, and GST = ₹180. A common mistake is to take 18% of ₹1,180 (₹212.40) – that is wrong, because the 18% was charged on ₹1,000, not on ₹1,180.
CGST, SGST and IGST explained
- CGST (Central GST) and SGST (State GST) apply when the seller and buyer are in the same state. The GST is split equally: at 18%, that is 9% CGST + 9% SGST. In Union Territories without a legislature, UTGST replaces SGST.
- IGST (Integrated GST) applies when goods or services go from one state to another, and on imports. The full rate is charged as IGST.
The total tax is the same either way – only the way it is shared between the Centre and the states changes.
Current GST rates in India
GST started on 1 July 2017 with four main slabs of 5%, 12%, 18% and 28%. From 22 September 2025, the GST Council simplified this to two main rates – 5% for many everyday goods and 18% as the standard rate – plus a special 40% rate for a small list of luxury and "sin" goods. Some items remain at special rates, such as 3% on gold and silver, and many essentials like fresh milk and vegetables are exempt (0%). Rates for specific items can change, so always check the latest notification on the official CBIC or GST portal, or ask your accountant, before filing returns.
Frequently asked questions
How do I calculate 18% GST on ₹1,000?
Multiply ₹1,000 by 18 and divide by 100 to get ₹180 GST. The total including GST is ₹1,180.
How do I remove GST from a price?
Multiply the GST-inclusive price by 100 and divide by (100 + GST rate). For ₹1,180 at 18%: 1,180 × 100 ÷ 118 = ₹1,000.
When is IGST charged instead of CGST and SGST?
IGST is charged when the supplier and the place of supply are in different states, and on imports. For sales within the same state, CGST and SGST are charged in equal halves.
Is this calculator suitable for filing returns?
It is a quick helper for invoices and price checks. For filing, always confirm the correct rate and HSN or SAC code for your item on the official GST portal.