How to add or remove GST
- Choose Add GST for a price before tax, or Remove GST for a price that already includes it.
- Enter the Amount and the GST rate: tap a common rate or type any rate, such as 3 or 0.25.
- Choose whether the sale is Within a state (CGST and SGST) or Between states (IGST), and read the tax and both prices.
The formulas
| To find | Formula | Example at 18% |
|---|---|---|
| Price including GST | price × (1 + rate ÷ 100) | ₹1,000 × 1.18 = ₹1,180 |
| GST on a price | price × rate ÷ 100 | ₹1,000 × 0.18 = ₹180 |
| Price before GST | inclusive price ÷ (1 + rate ÷ 100) | ₹1,180 ÷ 1.18 = ₹1,000 |
| GST inside an inclusive price | inclusive price × rate ÷ (100 + rate) | ₹1,180 × 18 ÷ 118 = ₹180 |
CGST and SGST or IGST
Whether a sale is within a state or between states decides how the tax is split, not how much it is. A shop in Pune selling to a customer in Mumbai charges 9% CGST and 9% SGST on an 18% item; the same shop selling to a buyer in Bengaluru charges 18% IGST. Businesses show these separately on a tax invoice, which is why the calculator lists them.
The 2025 rate changes
The GST Council cut the number of main rates in September 2025, moving most goods that were taxed at 12% and 28% into the 5% and 18% slabs, and created a 40% rate for a small group of items. Because the rates for individual items changed, older price lists and bills may not match today’s rates. For other countries’ sales taxes, use the VAT calculator or the sales tax calculator.