Add or remove GST instantly — with the CGST, SGST or IGST split and the formula.
How do you calculate GST?
GST is a percentage of the taxable value — the price before tax, after any discount shown on the bill. To add GST, multiply the taxable value by the rate. To remove GST from a price that already includes it (a reverse GST calculation), divide by (100 + rate) and multiply by 100.
Add GST: ₹1,000 at 18% → GST = 1,000 × 18 ÷ 100 = ₹180 → total ₹1,180 (CGST ₹90 + SGST ₹90).
Remove GST: ₹1,180 including 18% → taxable value = 1,180 × 100 ÷ 118 = ₹1,000 → GST = 1,180 − 1,000 = ₹180.
Odd paise: ₹999 including 5% → taxable value = 999 × 100 ÷ 105 = ₹951.43 → GST = 999 − 951.43 = ₹47.57 → CGST ₹23.79 + SGST ₹23.78.
Always work out the tax by subtraction (price − taxable value) when the price includes GST. Multiplying a rounded taxable value by the rate can leave the bill one paisa out, and the total on your invoice will not match the shelf price.
What are the GST slabs after GST 2.0?
The GST Council's GST 2.0 changes took effect on 22 September 2025 (Notifications 9/2025 and 10/2025-Central Tax (Rate)). The 12% and 28% slabs were removed.
| Rate | Typical goods and services |
|---|
| 0% | Fresh milk and UHT milk, paneer, bread and roti, fresh vegetables and fruit, eggs, salt, books, notebooks, pencils |
| 0.25% | Rough and cut diamonds, unset precious stones |
| 3% | Gold, silver, jewellery, imitation jewellery |
| 5% | Packaged food, ghee and butter, edible oil, tea, soap bars, toothpaste, shampoo, medicines, clothing and footwear up to ₹2,500, restaurant and salon services (without input tax credit) |
| 18% | Mobile phones, laptops, TVs, ACs, refrigerators, cement, paints, hardware, small cars, most professional services |
| 40% | Aerated and caffeinated drinks, larger cars, motorcycles above 350 cc; pan masala and tobacco from 1 February 2026 |
Not sure of an item's rate? Look it up in the HSN code finder, which lists the GST 2.0 rate against each code.
CGST and SGST or IGST — which one?
It depends on the place of supply. When the seller and the place of supply are in the same state, the GST is split equally: half as CGST (to the Centre) and half as SGST (to the state), or UTGST in a union territory. At 18% that is 9% + 9%. When the place of supply is in another state, the full rate is charged as IGST. A walk-in customer at your counter is always an intra-state sale.
Shop in Pune sells a ₹10,000 laptop to a customer in Pune → CGST ₹900 + SGST ₹900. Same laptop shipped to Indore → IGST ₹1,800.
Common GST calculation mistakes
- Taking 18% of an inclusive price. 18% of ₹1,180 is ₹212.40, not the tax inside it. The tax inside ₹1,180 is ₹180.
- Still using 12% or 28%. Those slabs ended on 22 September 2025; update your item rates.
- Rounding CGST and SGST separately. Round one half and give the remainder to the other, so the two always add up to the total tax.
- Charging GST before discount. Tax is on the value after a discount shown on the invoice.
- Charging GST without registration. Only a GST-registered business may collect GST. A composition dealer issues a bill of supply with no tax.
Need the bill itself? Make one with the free GST invoice generator, and check your customer's number with the GSTIN checker before you print it.
GST calculator — questions people ask
How do I calculate GST on an amount?
Multiply the amount before tax by the GST rate and divide by 100. At 18%, GST on ₹1,000 is ₹1,000 × 18 ÷ 100 = ₹180, so the customer pays ₹1,180. Inside one state the ₹180 is split into ₹90 CGST and ₹90 SGST; between states it is all IGST.
How do I remove GST from a price that already includes GST?
Divide the inclusive price by (100 + rate) and multiply by 100 to get the taxable value, then subtract it from the price to get the GST. For ₹1,180 at 18%: ₹1,180 × 100 ÷ 118 = ₹1,000 taxable value, and ₹1,180 − ₹1,000 = ₹180 GST. This is also called a reverse GST calculation.
What are the GST rates after GST 2.0?
From 22 September 2025 the main GST slabs are 0%, 5%, 18% and 40%. The 12% and 28% slabs were removed. Special rates of 3% for gold, silver and jewellery and 0.25% for rough and cut diamonds continue. Pan masala and tobacco moved to 40% from 1 February 2026.
When do I charge CGST and SGST, and when IGST?
Charge CGST plus SGST (or UTGST) when the seller and the place of supply are in the same state, for example a shop in Chennai selling to a customer in Tamil Nadu. Charge IGST at the full rate when the place of supply is in another state, such as goods delivered from Chennai to Bengaluru.
Why is CGST sometimes one paisa more than SGST?
When the total GST is an odd number of paise it cannot be split into two equal halves. This calculator rounds CGST to the nearest paisa and gives the remainder to SGST, so CGST plus SGST always equals the total GST exactly. ₹47.57 becomes ₹23.79 CGST and ₹23.78 SGST.
Are the 12% and 28% GST slabs still used?
No. Since 22 September 2025 goods that were at 12% moved mostly to 5%, and goods at 28% moved mostly to 18%, with a few luxury and sin goods going to 40%. Bills dated on or after that day must use the new rates, whatever rate is printed on old stock.
Is GST charged before or after a discount?
GST is charged on the transaction value after a discount that is shown on the invoice at the time of sale. If an item is ₹1,000 with a ₹100 discount, GST at 18% is on ₹900, which is ₹162. A discount given later needs a credit note to reduce the tax.
Does this GST calculator save or send my numbers?
No. The calculator runs entirely in your browser and works offline once the page has loaded. Nothing you type is sent to Billux or stored on a server. Use the Share link button if you want to send a calculation to someone; it puts the numbers in the link itself.