How to Calculate GST in India (with Examples)
Goods and Services Tax (GST) is charged on most goods and services sold in India. The common slabs are 0%, 5%, 18% and 40% after the 2025 rate rationalisation, plus special rates for items such as gold. Knowing how to add or remove GST lets you price products correctly and check invoices.
Adding GST to a price (exclusive)
GST amount = Price × Rate ÷ 100. Total = Price + GST amount.
Example: a service costs ₹10,000 at 18%. GST = 10,000 × 18 ÷ 100 = ₹1,800. Total invoice = ₹11,800.
Removing GST from a price (inclusive)
When a price already includes GST: Base price = Total × 100 ÷ (100 + Rate). GST = Total − Base.
Example: you paid ₹1,180 including 18% GST. Base = 1,180 × 100 ÷ 118 = ₹1,000, so GST = ₹180.
CGST, SGST and IGST
For a sale within the same state, GST is split equally into CGST and SGST (18% becomes 9% + 9%). For a sale to another state, the full rate is charged as IGST. The total tax is the same either way.
Common mistakes
- Applying the rate to an inclusive price, which overstates the tax.
- Using an old rate after a GST Council change.
- Charging CGST + SGST on an inter-state sale.
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Last updated: 2026-11-07