GST Calculator

Goods and Services Tax questions come in two shapes: adding tax to a price you have 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. 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. Note 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 is wrong by 162, because 18% was never charged on the gross figure — it was charged on the net.

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. The selector is the most important control on the page.

The CGST and SGST split

The result shows the tax divided into two equal halves — 450 and 450 on the example above. That split applies to an intra-state supply, where central and state governments each take half. On an inter-state supply the entire amount is IGST and there is no split at all, even though the total tax is identical. The tool shows the intra-state presentation; 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. It applies one rate to the whole amount.

Real invoices are frequently not like that. A bill carrying goods at 12% and services at 18% has to be calculated line by line and the tax totalled — running the invoice total through a single rate produces a figure that will not reconcile. If your invoice has mixed rates, calculate each block separately.

Three further things are outside the scope of this tool entirely:

• 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 rather than the supplier is liable for the tax.
• Input tax credit, which is what actually determines a registered business's cash outflow. The GST on your sales is not what you pay; what you pay is that figure less the credit on your purchases.

Because of the last point, treat this page as an invoicing aid, not a liability calculator. Your GSTR filings and your accountant are the authority on what is 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 displays rupees always. Showing an 18% GST figure with a dollar sign would imply a jurisdiction that does not exist.

Rounding on invoices

The tool carries paise through the calculation. Statutory rounding on the final invoice value follows the rules your accounting system applies, and a difference of a rupee between this page and your billing software is almost always a rounding convention rather than an arithmetic error.

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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.