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GST Calculator: Add or Remove GST
Work out GST on a price, or pull the GST out of an amount that already includes it. Handles CGST + SGST or IGST and several items at different rates, using the current slabs.
Taxable value
₹10,000.00
Total GST
₹1,800.00
CGST ₹900.00 + SGST ₹900.00
Total including GST
₹11,800.00
Rounded invoice total: ₹11,800.00
The two formulas
Adding GST (price before tax): GST = amount × rate ÷ 100, and total = amount + GST.
Removing GST (price includes tax): taxable value = amount × 100 ÷ (100 + rate), and GST = amount − taxable value.
Example at 18%: a ₹2,360 bill including GST has a taxable value of ₹2,360 × 100 ÷ 118 = ₹2,000, and GST of ₹360. Within a state, that's ₹180 CGST and ₹180 SGST.
What changed in September 2025
The GST Council's 56th meeting (3 September 2025) simplified the rate structure from 22 September 2025. The 12% and 28% slabs were dropped: most goods and services moved to 5% or 18%, and a 40% rate applies to a short list of luxury and demerit goods. Invoices dated before 22 September 2025 still use the old rates, which is why 12% and 28% are still available in the calculator.
Rates are set per HSN (goods) or SAC (services) code, and some items have special rates or exemptions. For anything you invoice regularly, confirm the rate against the official CBIC rate notifications or with your tax consultant.
Who should use this
- Small businesses and freelancers checking an invoice before sending it.
- Buyers who want to see how much of a bill is tax, for example for input tax credit.
- Anyone comparing prices quoted with and without GST.
This is a calculator, not tax advice. Registration thresholds, input tax credit and filing rules depend on your business, so speak to a GST practitioner for those.
Frequently Asked Questions
How do I calculate GST on an amount?
Multiply the taxable value by the rate. For ₹10,000 at 18%, GST is ₹1,800 and the total is ₹11,800. Choose 'Before GST' and the calculator adds it for you.
How do I remove GST from an inclusive price?
Divide by (1 + rate/100). For ₹11,800 including 18% GST: 11,800 ÷ 1.18 = ₹10,000 taxable value, so GST is ₹1,800. A common mistake is taking 18% of ₹11,800 (₹2,124), which overstates the tax.
What are the current GST rates?
Following the GST Council's rate rationalisation effective 22 September 2025, the main slabs are 0%, 5%, 18% and 40% (the 40% rate is for luxury and 'sin' goods), with special rates such as 3% for gold and jewellery and 0.25% for rough diamonds. The 12% and 28% slabs were removed, and most of those items moved to 5% and 18%. Always confirm the rate for a specific product or service by its HSN/SAC code.
When do I charge CGST + SGST, and when IGST?
For a sale within the same state (intra-state), the GST is split equally into CGST and SGST (or UTGST in a union territory). For a sale to another state (inter-state), the full amount is charged as IGST. The total tax is the same either way.
Why is the rounded total different?
Tax is calculated to the paisa on each item. Invoices are often rounded to the nearest rupee at the end, which is shown separately so you can match your billing software.