Type an amount, pick a rate, and see the tax and the total straight away. It works both ways: add GST to a base price, or strip GST out of a price that already includes it — which is the calculation most shopkeepers actually need, and the one that is easiest to get wrong by hand.
Adding GST is simple arithmetic: a ₹1,000 item at 18% becomes ₹1,180. Removing it is where people slip. To get the base price out of a ₹1,180 inclusive price you divide by 1.18 — you do not take 18% off ₹1,180, which would leave ₹967.60 and understate your taxable value by over ₹30.
The formula for a tax-inclusive price is:
This calculator does both and shows its working, so you can copy the taxable value straight onto an invoice.
The rate is the same either way; only the split changes, and it is decided by the place of supply, not by where the goods are made.
Getting this wrong does not change what the customer pays, but it does put the amount in the wrong box on your GSTR-1, and your buyer may not be able to claim the credit.
Most goods and services sit in one of five rates. 0% covers unbranded food staples, fresh produce and some books. 5% covers packaged food, economy transport and small restaurants. 12% covers processed food, business-class air travel and mobile phones. 18% is the default and covers most services, machinery and electronics. 28% covers luxury goods, air conditioners, and cars, which usually carry cess on top.
If you are not sure which slab an item falls in, look up its HSN code — the rate follows the code, not the trade name.
Divide the total by 1 plus the rate as a decimal. For 18%, divide by 1.18. For 5%, divide by 1.05. The answer is your taxable value, and the difference is the GST.
No. The arithmetic is identical; only the rate and the code differ. Services carry a SAC code instead of an HSN code, and most fall in the 18% slab.
Compare the place of supply with your own registered state. Same state means CGST and SGST at half the rate each; a different state means the full rate as IGST.
No. Cess applies to a short list of goods such as cars, tobacco and aerated drinks, and the rate varies by item, so it has to be added separately on the invoice.