How GST is Calculated

Learn how the Goods and Services Tax works in India, how to add GST to base prices, and how to reverse-calculate to find pre-tax prices.

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What is GST?

Goods and Services Tax (GST) is an indirect tax used in India on the supply of goods and services. It is a comprehensive, multi-stage, destination-based tax that replaced many former indirect taxes.

GST is generally divided into three categories: CGST (Central GST) and SGST (State GST) for transactions inside the state, and IGST (Integrated GST) for transactions between different states.

1. Adding GST to a Base Amount

To add GST to a base price, calculate the GST amount by multiplying the base price by the tax rate, then add that amount to the base price.

Formula:GST Amount = (Base Price × GST Rate) / 100 Total Price = Base Price + GST Amount

Practical Example:

If base price is ₹1,000 and GST rate is 18%: GST = (1,000 × 18) / 100 = ₹180. Total price = ₹1,000 + ₹180 = ₹1,180.

2. Removing GST (Reverse GST Calculation)

If you have a total price inclusive of GST and need to find the base pre-tax price, you cannot simply subtract the percentage. You must reverse the calculation.

Formula:Base Price = Total Price / (1 + (GST Rate / 100)) GST Amount = Total Price - Base Price

Practical Example:

If total price is ₹1,180 (inclusive of 18% GST): Base Price = 1,180 / 1.18 = ₹1,000. GST Amount = ₹180.

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