How to calculate GST
Adding GST to a price
GST amount = Price × GST rate ÷ 100, and Total = Price + GST.
Example: an item priced at ₹1,000 with 18% GST → GST is ₹1,000 × 18 ÷ 100 = ₹180, so the customer pays ₹1,180.
Removing GST from a price that already includes it
Price before GST = Inclusive price ÷ (1 + GST rate ÷ 100). For 18%, divide by 1.18; for 5%, divide by 1.05.
Example: ₹1,180 including 18% GST → ₹1,180 ÷ 1.18 = ₹1,000 before GST, and the GST inside it is ₹180. A common mistake is to take 18% of ₹1,180 (₹212.40) — that is wrong.
CGST, SGST and IGST — which one applies?
- Customer in the same state as you: the GST is split into two equal halves — CGST (Central) and SGST (State). 18% = 9% CGST + 9% SGST; 5% = 2.5% CGST + 2.5% SGST. On ₹1,000 at 18% that is ₹90 + ₹90.
- Customer in another state: the full rate is charged as IGST. On ₹1,000 at 18% that is ₹180 IGST.
The total tax is the same either way — only how it is shown on the bill changes.
Current GST rates (GST 2.0)
Since 22 September 2025, GST has four main slabs. The old 12% and 28% slabs were removed; most items in them moved to 5% or 18%.
| Rate | Typically covers |
|---|---|
| 0% (exempt) | Many basic essentials, such as most unpacked fresh food |
| 5% | Many everyday goods, and most restaurant food service |
| 18% | The standard rate — most goods and services |
| 40% | Luxury and "sin" goods |
A few special rates also exist (for example 3% on gold and 0.25% on rough diamonds). The rate for your item depends on its HSN/SAC code — always check the current rate on the official GST rates page.
Need to put this on a bill? Use our free GST invoice generator, or read what a GST invoice must include.
Frequently asked questions
How do I calculate 18% GST on ₹1,000?
18% of ₹1,000 is ₹180, so the total is ₹1,180. Within the same state that is ₹90 CGST + ₹90 SGST; for a customer in another state it is ₹180 IGST.
How do I remove GST from a price that includes it?
Divide the price by (1 + rate/100). For 18% GST divide by 1.18: ₹1,180 ÷ 1.18 = ₹1,000, so the GST inside is ₹180.
Is 12% or 28% GST still charged?
No. From 22 September 2025 (GST 2.0) the 12% and 28% slabs were removed. Most items moved to 5% or 18%, and some luxury and sin goods to 40%. Check the current rate for your HSN code on the GST portal.
What is the GST on restaurant food?
Most restaurants charge 5% GST (2.5% CGST + 2.5% SGST) without input tax credit. Restaurants inside hotels with room tariffs above ₹7,500 per night charge 18%. Check the current rule on the GST portal.
Is this GST calculator free?
Yes. It is free, needs no signup and works on your phone. Calculations happen in your browser.