How to Calculate GST: Add, Remove & Examples (Formula)

There are two things you need to do with GST: add it to a price (exclusive amount) or remove it from a price that already includes it (inclusive amount). The GST calculator does both in one click, and the formulas are below.

1. Add GST to a price

• GST amount = price × GST rate ÷ 100
• Total = price + GST amount

Example: price ₹10,000, GST 18%. GST = 10,000 × 18 ÷ 100 = ₹1,800. Total = ₹11,800.

2. Remove GST from a GST-inclusive price

• Original price = inclusive price × 100 ÷ (100 + rate)
• GST amount = inclusive price − original price

Example: inclusive price ₹11,800 at 18%. Original = 11,800 × 100 ÷ 118 = ₹10,000. GST = ₹1,800.

Common mistake: subtracting 18% of 11,800 (₹2,124) is wrong. The GST was calculated on the smaller base, so divide by 1.18 instead.

3. Split into CGST and SGST

For a sale within the same state, divide GST into two equal halves. At 18%, that is 9% CGST and 9% SGST. On ₹10,000 that is ₹900 each. For a sale to another state, charge the whole 18% as IGST (₹1,800). Read CGST, SGST and IGST explained.

Quick reference

For rates like 3% (gold) use 1.03. Check which rate applies to your item in GST rates in India.

Example with a discount and several items

Items: ₹6,000 at 18% and ₹4,000 at 5%. GST = 1,080 + 200 = ₹1,280. Total = ₹11,280. When items have different rates, calculate GST per line and add them up. Our invoice generator and quotation generator do this for you automatically for every line.

FAQs

Is GST calculated on the discounted price?

Generally yes. A discount given at the time of supply and shown on the invoice reduces the taxable value. Confirm special cases with your CA.

How do I find the GST rate?

It depends on the HSN or SAC code of the item. See HSN and SAC codes explained.