GST Calculator

Goods and Services Tax questions come in two shapes: adding tax to a price you've set, and pulling tax back out of a price that already includes it. They use different arithmetic, and mixing them up is the single most common invoicing error.

Adding GST

A taxable value of 500 at 18% gives GST of 90 and an invoice total of 590. It's straightforward multiplication:

GST = taxable value × rate ÷ 100
Invoice total = taxable value + GST

Removing GST

An inclusive price of 5,900 at 18% has a taxable value of 5,000 and GST of 900. Watch what happens if you take the obvious shortcut and subtract 18% of 5,900: you get 1,062 of tax and a taxable value of 4,838. That's out by 162, because the 18% was charged on the net figure in the first place, never on the gross.

Taxable value = inclusive price ÷ (1 + rate ÷ 100)

Set the action selector to Remove and the tool does this correctly. Set it to Add and it does the other one. Of all the controls on the page, that selector matters most.

The CGST and SGST split

The result shows the tax divided into two equal halves, 450 and 450 in the example above. That split applies to an intra-state supply, where the central and state governments each take half. On an inter-state supply the whole amount is IGST and there's no split at all, even though the total tax is identical. The tool shows the intra-state presentation, so read it accordingly if your supply crosses a state border.

Slabs and what sits outside them

The rate selector offers 5%, 12%, 18% and 28%, the four principal slabs, and applies one rate to the whole amount.

Real invoices often aren't that simple. A bill carrying goods at 12% and services at 18% has to be calculated line by line and the tax totalled. If you run the invoice total through a single rate, you'll get a figure that won't reconcile. So if your invoice has mixed rates, calculate each block separately.

The tool also doesn't handle any of these:

• Compensation cess, levied on top of GST on a defined list of goods including tobacco, aerated drinks and certain vehicles.
• Reverse charge, where the recipient, and not the supplier, is liable for the tax.
• Input tax credit, which is what actually determines a registered business's cash outflow. What you pay is the GST on your sales less the credit on your purchases.

Because of that last one, treat this page as an invoicing aid and don't use it as a liability calculator. Your GSTR filings and your accountant are the authority on what's owed.

Why the amounts stay in rupees

GST is an Indian tax with rates defined in Indian law, so this calculator ignores the site-wide currency selector and always shows rupees. An 18% GST figure with a dollar sign in front of it would imply a jurisdiction that doesn't exist.

Rounding on invoices

The tool carries paise through the calculation. Statutory rounding on the final invoice value follows whatever rules your accounting system applies. If this page and your billing software differ by a rupee, it almost always comes down to a rounding convention, and the arithmetic itself is fine.

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For single-rate value added tax outside India, use the VAT calculator. For US-style tax added at the register, use the sales tax calculator. To work out the pre-tax price you need in order to hit a margin, use the profit margin calculator.