GST Calculator

Goods and Services Tax is India’s main indirect tax on the supply of goods and services. It replaced a stack of separate central and state levies — excise, service tax, VAT, and a long tail of cesses and entry taxes — with a single tax charged at each stage of the chain, where each business can set the tax it paid on its inputs against the tax it collects on its outputs.

Indirect means the tax is collected by the seller and paid over to the government, rather than assessed on you directly. It appears on the invoice as a line, and the arithmetic of that line is what this calculator does.

It is worth being clear about the division of labour. The multiplication is exact and this page does it exactly. Which rate belongs to which supply, where the place of supply is, and what an invoice must contain are questions of classification and of the rules in force — none of which a calculator can answer.

So, plainly: this page is a calculator and its output is not tax advice. It does not know how your supply is classified, where your place of supply is, whether any credit is available to you, or what your filings require. Use it to check your own arithmetic, and take an actual position with a qualified professional and the current rules in front of you.

Four quantities do all the work:

• Taxable value — the amount the tax is charged on. For goods this is usually the price before tax; for a multi-line invoice it is quantity times unit price, computed per line.
• Rate — a percentage that comes from how the supply is classified, not from what it costs.
• GST amount — taxable value times rate, divided by a hundred.
• Final price — the taxable value plus the tax. This is what the buyer pays.

The part that makes GST different from a simple sales tax is what happens next. A registered business that paid GST on its own purchases can generally set that against the GST it collects, and pay over only the difference — so tax is effectively charged on the value each stage adds rather than compounding down the chain. That mechanism is Input Tax Credit, covered further down.

On a taxable value, GST is a single multiplication:

Intra-state, that ₹1,800 is shown as ₹900 of CGST and ₹900 of SGST — half the rate each. Inter-state it is ₹1,800 of IGST at the full rate. The total collected is identical either way; only the split changes.

Two formulas, one for each direction.

• The second formula divides. Taking the rate off the total is a different operation and gives a different answer — see the reverse section below for the size of the gap.
• The tax is always the difference between the two figures, never a second independent calculation. That is what makes the base and the tax add back to the total exactly.
• A 0% rate is a legitimate input, not an error. The tax is zero and the total is the base, in both directions.

Central Goods and Services Tax — the portion of GST that goes to the central government. On supplies treated as intra-state, GST is generally levied as CGST together with SGST, each at half the total rate. An 18% supply therefore carries 9% CGST and 9% SGST.

Whether a supply is treated as intra-state depends on the location of the supplier and the place of supply, both determined by the GST rules rather than by geography alone. The Intra-State option on this calculator decides how the tax is presented; it does not determine how a supply should be treated.

State Goods and Services Tax — the portion that goes to the state government, and the counterpart to CGST. The two are charged together on the same taxable value at the same rate, so from the buyer’s side the pair behaves exactly like one tax at the combined rate. In union territories, the equivalent component is UTGST.

Because they are always charged together, an invoice showing SGST without CGST (or the reverse) on the same line is a signal that something has gone wrong in the working.

Integrated Goods and Services Tax — a single component charged at the full rate on supplies treated as inter-state, instead of the two-part CGST and SGST split. An 18% inter-state supply carries 18% IGST and nothing else.

The buyer pays the same total either way. What differs is the split between governments and how the credit flows, which is why the distinction matters to the people filing returns rather than to the arithmetic of the invoice line.

This distinction causes more wrong GST figures than every rate question combined, and it is the reason this calculator makes you pick a mode instead of guessing from one amount box.

• GST-exclusive— the figure shown does not include tax. GST goes on top and the buyer pays more than the number quoted. Business-to-business quotes are commonly exclusive, and usually say “plus GST”.
• GST-inclusive — the figure shown already contains the tax. The taxable value is smaller than the number quoted. Retail prices to consumers are commonly inclusive.

The same ₹11,800 means two entirely different things depending on which it is. As an exclusive price it becomes ₹13,924 once 18% is added. As an inclusive price it is already the total, and the taxable value behind it is ₹10,000. If you are unsure which you are looking at, run the reverse calculation and see whether the base that comes out is a plausible price.

Multiply the taxable value by the rate, divide by a hundred, and add the result back on. In the calculator: choose Add GST, type the amount before tax, pick the rate.

Divide the inclusive price by (100 + rate) and multiply by 100. Equivalently, divide by 1.18 for an 18% rate. The tax is whatever is left over.

The tempting shortcut — take 18% of ₹11,800 — gives ₹2,124, which is ₹324 too much. The rate was never applied to the total; it was applied to the base, and the base is smaller. A quick sanity check: at an 18% rate the tax is about 15.25% of the inclusive price, not 18%. The general form of that trap — recovering an original figure from one that already includes an increase — is what the percentage calculator covers, for any rate rather than the GST slabs.

The same division at each rate. Every row below is computed by the calculator on this page.

Enter ₹1,000 in Add GST mode and pick a rate. Every configured slab comes to:

Enter ₹5,000 in Add GST mode and pick a rate. Every configured slab comes to:

Enter ₹10,000 in Add GST mode and pick a rate. Every configured slab comes to:

Enter ₹1,00,000 in Add GST mode and pick a rate. Every configured slab comes to:

An invoice with several lines is the same arithmetic repeated, with one rule that cannot be broken: each line is taxed at its own rate, and the totals are the sum of the lines.

The wrong way is to add the taxable values first and apply one averaged rate to the sum. With a 5% line and a 28% line there is no meaningful average, and the figure that comes out misstates both. The Multiple items tab computes every line independently for exactly this reason.

A word on what this is not. Calculating the taxable value, the components and the invoice value is the arithmetic part of an invoice. An actual tax invoice must satisfy legal requirements this tool does not attempt — supplier and recipient details, registration numbers, an invoice number and date, HSN or SAC codes, place of supply and more. The CSV export is a working document, not a compliant invoice.

Input Tax Credit is the mechanism that stops GST compounding at every stage of a supply chain. In outline: a registered business pays GST on what it buys and collects GST on what it sells, and can generally set the first against the second, paying over only the difference. The effect is that tax lands on the value each stage adds rather than on the full price at every stage.

A simplified illustration. A trader buys goods for ₹10,000 plus ₹1,800 of GST, and sells them for ₹15,000 plus ₹2,700. Setting the tax paid against the tax collected leaves ₹900 to pay over — which is 18% of the ₹5,000 of value the trader added. Working out that added value as a mark-up on the purchase price is a plain percentage increase, and is a separate question from the tax on it.

That is the concept and nothing more. Whether a credit is actually available in a given case depends on registration, on the nature of the purchase, on conditions and restrictions in the rules, and on the supplier having done their part. This page cannot tell you whether you are eligible for anything, and does not try.

• Treating an inclusive amount as exclusive. The most expensive mistake on this list, and the easiest to make from a price tag that does not say which it is.
• Taking the rate off the total to reverse it. 18% of ₹11,800 is ₹2,124, not ₹1,800. Divide by 1.18 instead.
• Applying the wrong rate. The rate follows the classification of the supply, never its price and never what a similar-looking product carries.
• Forgetting to split CGST and SGST on a supply presented as intra-state, or showing one without the other.
• Using IGST where the supply needs the other treatment, or the reverse. The total is the same, so the error survives a check that only looks at the bottom line.
• Rounding too early. Round once, at the end, and derive the components from the rounded total — otherwise CGST plus SGST stops equalling the total GST and the invoice fails its own arithmetic.
• Confusing the GST amount with the invoice total. One is the tax; the other includes it.
• Assuming one rate covers a whole invoice. Mixed-rate invoices are ordinary, and an averaged rate across them is wrong.
• Treating a calculator’s output as tax advice. It is arithmetic to check your working against, nothing more.

All illustrative, all computed by the engine on this page.

Everything runs locally in your browser. Your calculation data is not uploaded to our server, not stored, and not sent to an analytics endpoint. There is no account to create because there is nothing being kept — the calculation is JavaScript running on your own machine, and closing the tab is the whole of the deletion process.

The one exception is one you control. The share button puts the amount, rate and mode into the URL and hands you the link; the figures travel inside it, so you can read exactly what you are about to send. Line items are deliberately left out of the link — item names are the one field where somebody might type something they would rather not paste into a chat window. Downloads and printing are the same: the file is produced in the browser and saved to your own disk.