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When you transact within the same state (intra-state), GST is split equally into CGST (Central) and SGST (State). For inter-state transactions, the full GST is charged as IGST.
Example at 18% GST: Intra-state → CGST 9% + SGST 9%. Inter-state → IGST 18%.
Common goods and services by GST category
| GST Rate | Common Items |
|---|---|
| 0% | Essential food items, healthcare, education, fresh vegetables, milk |
| 3% | Gold, silver, jewellery, precious stones |
| 5% | Packaged food, newspapers, economy class air travel, tea, coffee |
| 12% | Smartphones, computers, business class travel, butter, cheese |
| 18% | Most services (restaurants, IT, banking), electronics, AC, refrigerators |
| 28% | Luxury items, tobacco, aerated drinks, automobiles, 5-star hotels |
Almost every mistake with GST comes from confusing two different questions. Adding GST starts from a price that does not yet include tax and works forward. Removing GST starts from a price that already includes tax and works backward. The arithmetic is not symmetrical, and using the wrong one produces an error that grows with the rate.
To add GST, multiply the base amount by the rate and add it on. To remove GST, divide the inclusive amount by one plus the rate; you cannot simply subtract the percentage. This is the single most common GST error in day-to-day billing.
A service is priced at ₹10,000 before tax and attracts 18% GST. The tax is ₹1,800 and the invoice total is ₹11,800. If the supplier and the customer are in the same state, that ₹1,800 splits into CGST of ₹900 and SGST of ₹900. If they are in different states, it is a single IGST line of ₹1,800.
You receive a bill for ₹11,800 inclusive of 18% GST and need the taxable value. Divide by 1.18 to get ₹10,000, and the tax component is the remaining ₹1,800. The tempting shortcut of taking 18% of ₹11,800 gives ₹2,124, which is wrong by ₹324. At 28% the same mistake is far larger: 28% of an inclusive ₹12,800 is ₹3,584, whereas the correct tax component is ₹2,800.
India operates a dual GST, so the same total rate is collected differently depending on where the supply moves. The total the customer pays is identical either way; only the split changes.
| Type of supply | What appears on the invoice | Example at 18% |
|---|---|---|
| Intra-state (within the same state) | CGST + SGST, each half the total rate | 9% CGST + 9% SGST |
| Intra-union territory | CGST + UTGST, each half the total rate | 9% CGST + 9% UTGST |
| Inter-state (across states) | IGST at the full rate | 18% IGST |
Which one applies is decided by the place of supply, not by where the invoice is printed or where payment is made. For goods this is usually where the movement ends; for services the rules vary by category and are worth checking for anything unusual such as immovable property, transport or online services.
GST is charged in bands rather than at one universal rate, which is why a single bill can carry several different rates across its line items.
| Rate | Typically covers |
|---|---|
| 0% / exempt | Most unbranded staple foods, fresh produce, and certain essential services |
| 5% | Common household necessities, many transport services and economy categories |
| 12% | Processed foods and a range of mid-tier goods |
| 18% | The broadest band, covering most services and many manufactured goods |
| 28% | Luxury and demerit categories, sometimes with an additional compensation cess |
Classification is specific to the HSN or SAC code of what you are selling, and rates are revised periodically by the GST Council. Treat the table above as orientation rather than authority, and confirm the current rate for your exact code before issuing an invoice.
Tax amounts on an invoice are normally rounded to two decimal places per line, and the final payable is commonly rounded to the nearest rupee with the difference shown as a separate rounding line. Rounding each line versus rounding only the total can produce a difference of a rupee or two on a long invoice, which is harmless commercially but causes reconciliation noise if your accounting software and your customer's do it differently.
Some items in the 28% band carry a compensation cess on top of GST, calculated on the same taxable value. This calculator handles the GST component only; if your product attracts cess you will need to add it separately. Businesses registered under the composition scheme pay a flat percentage of turnover instead of charging GST on invoices, so this calculator does not describe their position either.
GST is designed so that businesses ultimately pay tax only on the value they add. Tax paid on eligible business purchases can be set off against tax collected on sales, so the amount actually remitted is the difference. This is why the tax split on your invoice matters for your customer as well as for you, and why getting the intra-state versus inter-state classification right is more than a formatting detail. Credit is subject to conditions, including the supplier having actually reported the invoice, and several categories are specifically blocked.
Invoice values, client pricing and margins are commercially sensitive, and there is no reason for any of it to be sent somewhere to have a percentage applied. Every figure you enter on this page stays in your browser. The calculation runs locally in JavaScript, nothing is uploaded to a server, nothing is stored between visits, and no amount you type is attached to an analytics event. The page keeps working with your network disconnected, which is the easiest way to confirm it for yourself.
Divide the inclusive amount by one plus the rate. For 18% GST, divide by 1.18; for 5%, divide by 1.05. Subtracting the percentage directly from the inclusive price is the most common GST error and overstates the tax. On ₹11,800 inclusive of 18%, the taxable value is ₹10,000 and the tax is ₹1,800, not ₹2,124.
The total rate is the same, only the split changes. Supplies within a state are billed as CGST plus SGST, each half the total rate. Supplies across states are billed as a single IGST line at the full rate. Which applies is determined by the place of supply, not by where the invoice is raised.
The main bands are 0% or exempt, 5%, 12%, 18% and 28%, with an additional compensation cess on some items in the highest band. The correct rate depends on the specific HSN or SAC code of what you are supplying, and rates are revised periodically by the GST Council, so confirm the current rate for your code before invoicing.
Yes. GST is applied per line item, so a single invoice can carry several different rates if it covers goods or services in different bands. Each line is taxed on its own taxable value and the amounts are then totalled.
Tax is normally computed to two decimal places per line, with the final payable rounded to the nearest rupee and the adjustment shown separately. Rounding every line versus rounding only the total can differ by a rupee or two on long invoices, which is worth standardising with your accounting software.
No. The calculation runs entirely in your browser on your own device. Nothing you type is uploaded, stored or logged, and the page continues to work with your internet connection turned off.
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