- Price before GST
- ₹1,000.00
- CGST (9%)
- ₹90.00
- SGST (9%)
- ₹90.00
- Total GST
- ₹180.00
- Price with GST
- ₹1,180.00
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Please note: this calculator is a free aid for working out numbers, not financial, tax or investment advice. It has not been prepared or checked by a chartered accountant or financial adviser, and results may be inaccurate for your situation. Check important decisions with a qualified professional.
How to use GST Calculator
- Choose Add GST if your amount is the price before tax, or Remove GST if it already includes tax.
- Enter the amount and pick a GST rate, or type any other rate.
- Choose within a state (CGST + SGST) or between states (IGST) to see how the tax is split.
How GST is calculated
Adding GST: tax = price × rate ÷ 100, and the final price is the price plus the tax.
Removing GST from an inclusive price: price before tax = inclusive price ÷ (1 + rate ÷ 100). Subtracting 18% from the inclusive price is a common mistake: it gives the wrong answer because the 18% was charged on the smaller, pre-tax amount.
For a sale within one state the tax is split equally into CGST and SGST. For a sale from one state to another the whole amount is IGST.
Worked example
An item priced at ₹1,000 with 18% GST: tax is ₹180, so the customer pays ₹1,180. Within a state that is ₹90 CGST and ₹90 SGST; between states it is ₹180 IGST.
Going the other way, an invoice total of ₹1,180 at 18% means a pre-tax price of 1,180 ÷ 1.18 = ₹1,000, not ₹1,180 − 18% = ₹967.60.
Frequently asked questions
Which GST rate applies to my product or service?
Rates depend on the HSN or SAC code of the item. The buttons show the common slabs after the September 2025 rate changes; always confirm the current rate for your item on the official GST portal or with your accountant.
What is the difference between CGST, SGST and IGST?
CGST and SGST are the central and state shares on a sale within one state, each half of the total rate. IGST is charged on sales between states and goes to the centre, which shares it with the destination state.
Why can't I just subtract 18% to remove GST?
Because GST was added on the pre-tax price. Dividing by 1.18 reverses it exactly; subtracting 18% of the inclusive price removes too much.
Is this a substitute for professional tax advice?
No. It does the arithmetic correctly, but questions about input tax credit, composition schemes or exemptions need a qualified professional.