GST Calculator

The calculator updates as you type. Decide first whether your amount is before tax or after tax, because that sets the direction of the calculation.

1. Open Calculate and choose Add GST to a price if your amount is before tax, or Remove GST (the price includes it) if your amount is a total that already contains the tax.
2. Type the figure in Amount. The default is 1000.
3. Type the rate in GST rate (%). It is a free number field with a default of 18, so enter the rate that applies to your item or service, not a decimal such as 0.18.
4. In Show the split as, choose Same state (CGST + SGST) or Another state (IGST).
5. Read the price before GST, the total GST, the price with GST and the split rows, then check the formula line to see the working.

The right rate depends on the item or service and is set by notification. The tool does not know which rate applies to your goods, and it does not list rate slabs, so check the official rate schedule or your invoice.

Adding tax is a straight percentage of the price. Removing it is a division, and that is where most mistakes happen.

Adding. Take 1,000 at 18 percent. GST is 1,000 x 18 / 100 = 180, so the price with GST is 1,180. In the same-state view the tool shows CGST of 90 and SGST of 90, each at 9 percent.

Removing. Take a total of 1,180 that includes 18 percent. The price without GST is 1,180 / 1.18 = 1,000 and the GST inside it is 180. A second example: a total of 2,360 at 18 percent divides by 1.18 to give 2,000, with 360 of GST.

The common error is to take 18 percent of the total and subtract it. That gives 1,180 x 0.18 = 212.40, and 1,180 - 212.40 = 967.60, which is wrong by more than 32 because the 18 percent was charged on the base price, not on the total. The same logic applies to any rate, and to other sales taxes. For other rates and labels, the VAT and sales tax calculator uses the same arithmetic.

As general information, a supply within one state or union territory with a legislature carries CGST and SGST, which are each half of the rate. A supply between states carries IGST, the full rate. The total tax on a given price is the same either way, so the split is a presentation choice in this tool: the rows change, the total does not. For union territories without a legislature, the tool labels the second half as SGST or UTGST.

The calculator accepts any rate, so you can use it for a VAT-like tax in another country, but the CGST, SGST and IGST labels are Indian and will not fit other systems. Amounts are rounded to two decimals, so an invoice produced by accounting software may differ from the tool by a paisa or a cent.

This is arithmetic, not tax advice. Questions about input credit, filing returns, exemptions and which rate applies to your supply are separate topics for an accountant or the official tax department.

Several jobs sit next to a GST calculation. Adding a tax is a percentage increase, and the percentage increase calculator shows how much a value rose and by what percent. Taking a discount off a price is a percentage decrease, covered by the percentage decrease calculator, and the discount calculator turns an original price and a discount into a sale price. If the order of discount and tax matters to you, check how your invoice applies them, then run each step in turn.

For any other percentage of an amount, the percentage calculator is the general tool. If you sell goods and want to know what is left after costs, enter the pre-tax price, because tax collected is not income, in the profit margin calculator.

Two habits help. First, write down whether each figure on a quote is before or after tax, since a total that includes GST is easy to mistake for a base price. Second, keep the unrounded numbers until the last step, and round only the final invoice line, so small errors do not add up across many items.