GST Calculator: How to Add and Remove GST (With Examples)

GST trips people up because the same rate works two different ways: adding tax to a base price, and pulling tax out of a price that already includes it. Mixing them up over- or under-charges customers.

Adding GST (exclusive amount)

When your price is before tax, GST is added on top. At 18% on a 1,000 base: GST = 180, total = 1,180. The GST calculator does this in "add" mode and also splits the tax into CGST and SGST (9% + 9% for intra-state) automatically.

Removing GST (inclusive amount)

When a price already includes GST and you need the base, you cannot just subtract 18%. To remove 18% from a 1,180 total: base = 1,180 ÷ 1.18 = 1,000, so GST = 180. Use the calculator's "remove" mode — this is the part most manual calculations get wrong.

The CGST/SGST vs IGST split

For sales within a state, GST splits equally into CGST and SGST. For inter-state sales it is a single IGST at the full rate. The total tax is identical either way; only the labelling on the invoice changes.

Common GST rates to remember

India's slabs are 0%, 5%, 12%, 18% and 28%. Most services and many goods sit at 18%. When in doubt, check the rate for your specific HSN/SAC code rather than guessing.

Beyond GST

Outside India, the VAT calculator does the same job for value-added tax. Running a business? Pair GST math with the profit margin calculator to price correctly after tax, and generate a clean bill with the invoice generator.