How GST is calculated
GST is charged as a percentage of the taxable value of a supply. There are two common situations:
| You have | Formula | Example at 18% |
|---|---|---|
| Price before GST | GST = price × rate ÷ 100 | ₹10,000 → GST ₹1,800 → total ₹11,800 |
| Price including GST | GST = price × rate ÷ (100 + rate) | ₹11,800 → GST ₹1,800 → base ₹10,000 |
CGST, SGST and IGST
For a supply within one state, the GST is split in half: at 18%, that is 9% CGST and 9% SGST. For a supply from one state to another, the full 18% is charged as IGST. The calculator shows the split for you.
GST slabs in 2026
Since 22 September 2025, the main slabs are 0%, 5%, 18% and 40%. Gold and jewellery are at 3%, and rough diamonds at 0.25%. Some items, such as specified bricks and tiles, still carry 12%. Check the rate for your HSN or SAC code in the official CBIC notifications before you invoice.
VAT in the Gulf
The same calculator works for VAT: the UAE and Oman charge 5%, Saudi Arabia 15% and Bahrain 10%. There is no CGST/SGST split under VAT, so you see a single tax figure.
Frequently asked questions
How do I calculate GST on a price?
For a price that excludes GST, multiply it by the GST rate. For example, 18% GST on ₹10,000 is ₹1,800, making the total ₹11,800. For a price that already includes GST, the GST part is price × rate ÷ (100 + rate), so ₹11,800 including 18% GST contains ₹1,800 GST.
When is CGST + SGST charged and when is IGST charged?
When the supplier and the place of supply are in the same state or union territory, the tax is split equally into CGST and SGST (or UTGST). When they are in different states, or the supply is an import or export, the full rate is charged as IGST.
What are the GST rates in 2026?
Since 22 September 2025 the main GST slabs are 0%, 5%, 18% and 40%, with special rates such as 3% for gold and jewellery and 0.25% for rough diamonds. Always confirm the rate for your HSN or SAC code from the official CBIC notifications.
Does this calculator work for VAT in the UAE and Saudi Arabia?
Yes. Choose the country and the standard VAT rate is filled in for you: 5% for the UAE and Oman, 15% for Saudi Arabia and 10% for Bahrain. You can also type any custom rate.
Is my data saved or sent anywhere?
No. The calculation runs entirely in your browser. Nothing you type is sent to QuantProc or stored.
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