How to Calculate GST in India (Add or Remove GST)
Short answer
To add GST, multiply the price by the rate: ₹1,000 at 18% = ₹180 GST, total ₹1,180. To remove GST from an inclusive price, divide by (1 + rate): ₹1,180 ÷ 1.18 = ₹1,000 before tax. Within a state the GST is split equally into CGST and SGST; between states it is charged as IGST. Our GST calculator shows all the parts.
Goods and Services Tax (GST) is charged on most sales of goods and services in India. Shoppers want to know how much tax is inside a bill, and small businesses need correct invoice figures. The maths is the same as any percentage, with one twist when you take tax out of a price.
What are the GST rates in 2026?
Since 22 September 2025, following the GST Council's rate rationalisation, most items fall into two main slabs: a 5% merit rate and an 18% standard rate. A special 40% rate applies to a short list of luxury and sin goods and services. Some essentials are exempt (0%), and a few items such as gold have their own special rates. The rate for any item depends on its HSN or SAC code, so confirm it in the official CBIC rate list linked below.
How do I add GST to a price?
GST amount = net price × rate ÷ 100. Total = net price + GST.
| Net price | Rate | GST | Total | CGST + SGST (same state) |
|---|---|---|---|---|
| ₹1,000 | 18% | ₹180 | ₹1,180 | ₹90 + ₹90 |
| ₹2,500 | 5% | ₹125 | ₹2,625 | ₹62.50 + ₹62.50 |
How do I remove GST from an inclusive price?
This is where people slip. You cannot take 18% off the total, because the tax was calculated on the smaller net amount. Divide instead:
Net price = inclusive price ÷ (1 + rate/100). GST = inclusive price − net price.
Example: a ₹5,000 bill that includes 18% GST. ₹5,000 ÷ 1.18 = ₹4,237.29 before tax, so the GST inside it is ₹762.71. Taking 18% straight off ₹5,000 would wrongly give ₹900. Choose "remove GST" in the GST calculator to do this in one step.
CGST, SGST and IGST explained
- Intra-state sale (seller and buyer in the same state): the rate is split in half. 18% becomes 9% CGST + 9% SGST (or UTGST in a union territory).
- Inter-state sale: the full rate is charged as IGST. 18% stays 18% IGST.
The total tax is the same either way; only the split on the invoice changes.
To find what share of a final bill is tax, the percentage calculator is handy: on a ₹1,180 bill with 18% GST included, the ₹180 tax is about 15.25% of the total, not 18%.
GST and discounts
If a discount is shown on the invoice at the time of sale, GST is normally charged on the discounted price. So a ₹2,000 item with 10% off at 18% GST is ₹1,800 + ₹324 = ₹2,124. Work out the sale price first with the discount calculator, then add GST. Our guide to discounts and sale prices covers stacked offers.
Is GST like sales tax or VAT?
Yes, in the way it is calculated. US sales tax is added at the till, and UK VAT uses the same "divide by 1.2" trick to remove 20%. GST in India works like VAT: registered businesses can usually claim input tax credit for GST paid on their purchases.
Tips for small businesses
- Price products so the margin survives tax: see profit margin vs markup.
- Round only at the end. Rounding CGST and SGST separately can create a one-paisa difference.
- Keep the HSN/SAC code on every invoice line and confirm the rate before you bill.
Disclaimer: this guide is general information, not financial, tax, legal or medical advice. ViralScopeHub is not responsible for decisions made using it; rules and rates change, so confirm with the official source or a qualified professional.
Last updated: October 16, 2026, 8:55 AM ET. Reviewed against the sources listed below.
Frequently asked questions
How do I calculate 18% GST on an amount?
Multiply the amount by 0.18 for the tax, or by 1.18 for the total. ₹1,000 becomes ₹180 GST and ₹1,180 in total.
How do I remove GST from a total?
Divide the total by 1 plus the rate. For 18%, divide by 1.18. ₹1,180 ÷ 1.18 = ₹1,000 before GST.
What are the main GST slabs now?
Since 22 September 2025 the main slabs are 5% and 18%, with a 40% rate for selected luxury and sin goods. Some items are exempt or have special rates.
What is the difference between CGST, SGST and IGST?
CGST and SGST each take half the rate on sales within one state. IGST is the full rate on sales between states.
Is GST charged before or after a discount?
A discount shown on the invoice at the time of sale usually reduces the taxable value, so GST is charged on the discounted price.
