GST formulas
Adding GST to a price before tax:
Total = Price + GST
Removing GST from a price that already includes it (reverse GST):
GST = Total − Price before GST
Example: a total of ₹11,800 at 18% → price before GST = 11,800 × 100 ÷ 118 = ₹10,000, and GST = ₹1,800. A common mistake is taking 18% of ₹11,800 (₹2,124); that's the GST on the wrong base.
GST rates in India (GST 2.0)
From 22 September 2025, the GST Council replaced the four main slabs (5%, 12%, 18%, 28%) with two main rates and a special rate:
| Rate | Applies to (examples) |
|---|---|
| 0% | Essentials such as fresh food, milk, many health and education services |
| 5% | Everyday goods and some services, e.g. many packaged foods, and restaurants (without input tax credit) |
| 18% | The standard rate: most goods and most services, including IT, consulting, telecom and professional services |
| 40% | Luxury and "sin" goods and services, e.g. some tobacco products, aerated sugary drinks, premium cars and betting |
| 3% / 0.25% | Gold, silver and jewellery (3%); cut and rough diamonds (0.25%) |
Rates depend on the exact HSN or SAC code, so check yours on the CBIC rate finder before invoicing.
CGST, SGST, UTGST and IGST
- Within a state: the GST is split equally into CGST (to the Centre) and SGST (to the state). At 18%, that's 9% + 9%. In a Union Territory without a legislature, UTGST replaces SGST.
- Between states, or imports: the full rate is charged as IGST, for example 18% IGST.
- Exports: zero-rated. Supplies under a Letter of Undertaking (LUT) carry no GST.
The total tax is the same either way; only the split, and who collects it, changes. Which applies depends on the place of supply compared with the supplier's location.
Rounding
The calculator rounds to the paisa. On a GST invoice, each tax amount is usually rounded to two decimals, and the invoice total may be rounded to the nearest rupee with a separate "round off" line. To make an invoice with these numbers, use the GST invoice generator.
Frequently asked questions
How do I calculate 18% GST on an amount?
How do I remove 18% GST from a total?
Is the 12% and 28% GST slab gone?
What is the GST rate for IT and software services?
What is the difference between CGST + SGST and IGST?
Last updated . How we check our tools. Sources: GST Council (56th meeting, rates effective 22 Sep 2025).