GST Calculator

How GST is added and removed

Goods and Services Tax (GST) is a percentage added to the price of most goods and services in India. Businesses often need to do the calculation in two directions: add GST to a base price, or work backwards from a GST-inclusive price to find the original amount and the tax inside it.

The formulas

• Add GST: GST amount = Price × Rate ÷ 100, and Final price = Price + GST amount.
• Remove GST: Original price = Final price × 100 ÷ (100 + Rate), and GST amount = Final price − Original price.

Worked example

A product costs ₹1,000 before tax and attracts 18% GST. The GST is ₹180 and the customer pays ₹1,180. Going the other way, if a bill shows ₹1,180 inclusive of 18% GST, the original price is 1,180 × 100 ÷ 118 = ₹1,000 and the tax is ₹180. Many people wrongly subtract 18% from ₹1,180, which gives ₹967.60 and is incorrect, because the 18% applies to the original price, not the final price.

CGST, SGST and IGST

For a sale within one state, the GST is split equally between the Centre (CGST) and the State (SGST). On an 18% GST sale, that is 9% CGST plus 9% SGST. For a sale between states, the whole 18% is charged as IGST. The total tax is the same either way.

Frequently asked questions

Which GST rate applies to my product?

Rates depend on the item or service and are set by the GST Council, and they can change. Check the current rate for your HSN or SAC code on the official GST portal before invoicing.

Can I claim input tax credit?

Registered businesses can generally claim credit for GST paid on business purchases, subject to the conditions in the GST law. Speak to a chartered accountant for your situation.