What is GST Calculator India?

A GST calculator works out the Goods and Services Tax on an amount, either by adding GST to a base price (exclusive → inclusive) or by extracting GST already built into a price (inclusive → exclusive). Enter an amount and a GST rate, choose whether you're adding or removing tax, and the calculator shows the tax amount, the CGST/SGST or IGST split, and the final total.

GST (Goods and Services Tax) is charged in India at rates such as 5%, 12%, 18% and 28%, depending on the category of goods or services. This calculator handles both common scenarios: adding GST to a price that doesn't yet include tax, and working out how much GST is already included in a price that does.

How to Use This Calculator

Enter the base amount in rupees.
Choose a GST rate from the dropdown, or enter a custom rate.
Select Add GST if your amount excludes tax, or Remove GST if it already includes tax.
Click Calculate GST to see the tax amount, CGST/SGST split (for intra-state supply) and the final total.

How the Calculation Works

Add GST (exclusive → inclusive):
GST Amount = Original Amount × (GST Rate / 100)
Total = Original Amount + GST Amount

Remove GST (inclusive → exclusive):
Original Amount = Total ÷ (1 + GST Rate / 100)
GST Amount = Total − Original Amount

For an intra-state sale, GST is split equally into CGST and SGST (each half the total GST rate). For an inter-state sale, the full amount is charged as IGST instead.

Worked Example

A base price of ₹10,000 at 18% GST (Add GST mode): GST = ₹10,000 × 18% = ₹1,800. Total payable = ₹11,800. Since this is an intra-state supply, CGST = ₹900 and SGST = ₹900.

Who Should Use This

Useful for shop owners pricing invoices, freelancers quoting GST-inclusive fees, and shoppers who want to check whether a listed price already includes tax.

Important Considerations

GST rates differ by HSN/SAC code and can change through government notifications. This tool applies whatever rate you select — always confirm the correct rate for your specific goods or service on the official GST portal before filing.

Common Mistakes

The most common error is applying the "Add GST" formula to a price that already includes tax (or vice versa), which double-counts or under-counts tax. Always confirm whether your starting amount is inclusive or exclusive of GST first.

References

Official rates: CBIC GST Portal.

Frequently Asked Questions

What GST rates does this calculator support?

You can pick common Indian GST slabs — 5%, 12%, 18% and 28% — or enter any custom rate that applies to your goods or service.

How is CGST and SGST split calculated?

For sales within the same state, the total GST is split equally into CGST and SGST. For sales between different states, the full amount is charged as IGST instead of a CGST/SGST split.

Does this calculator file my GST return?

No. This is a calculation tool only. GST returns must be filed on the official GST portal.