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ToolBoxGenie

GST Calculator

Calculators · Added 3 July 2026

Work out GST in either direction: add tax to a net price to get the invoice total, or strip tax out of a gross amount you have already been charged. Standard slabs are one click away, and any custom rate can be typed in.

Direction

How to use the gst calculator

  1. 1Choose whether you are adding GST to a net amount or removing it from a gross total.
  2. 2Enter the amount.
  3. 3Pick a standard rate or type a custom percentage.
  4. 4Read the net, GST and gross figures — the CGST/SGST halves are shown for intra-state supply.

Examples

Adding GST to a quote

Input
Net 15,000 at 18%
Result
GST 2,700 (CGST 1,350 + SGST 1,350) · Gross 17,700

Extracting GST from a receipt

Input
Gross 5,900 at 18%
Result
Net 5,000 · GST 900

Divide by 1.18 — subtracting 18% of 5,900 would give the wrong answer.

About the gst calculator

Inclusive and exclusive pricing

The single biggest source of GST errors is ambiguity about whether a quoted price already contains the tax. 'Exclusive' pricing quotes the net and adds tax at invoice time — normal in business-to-business dealings, where the buyer reclaims it anyway. 'Inclusive' pricing quotes the total a consumer will actually pay, which is what retail display rules generally require.

When a purchase order says 15,000 and the invoice says 17,700, nobody has cheated anyone — one figure is exclusive and the other inclusive. Stating which basis you are using on every quote eliminates the argument entirely.

Why the reverse calculation catches people out

Tax is levied on the net amount, so it is 18% of the smaller number, not of the total. In a gross of 5,900, the tax component is 900 — which is 18% of 5,000 but only about 15.25% of 5,900. Anyone who subtracts 18% of the gross arrives at 4,838 instead of 5,000 and understates their revenue by 162 on every single line.

The reliable method is always division: net = gross ÷ (1 + rate). It works for every rate and never drifts.

Frequently asked questions

How do I remove GST from an inclusive price?
Divide the gross amount by (1 + rate ÷ 100). For an 18% rate, divide by 1.18. The GST component is the gross minus that result. Subtracting 18% directly from the gross is a frequent and expensive mistake.
What is the difference between CGST, SGST and IGST?
For a supply within a single state the tax is split evenly between central GST and state GST — an 18% rate becomes 9% CGST plus 9% SGST. For an inter-state supply the whole 18% is charged as a single integrated GST. The total paid is identical either way; only the allocation differs.
Which rate applies to my product?
Rates are set per HSN/SAC code and change from time to time. Common slabs are 5%, 12%, 18% and 28%, with 3% for gold and some categories exempt or zero-rated. Check the current notification for your specific code — this calculator does the arithmetic, not the classification.
Can I use this for VAT or sales tax?
Yes. The maths for any single-rate value-added tax is identical. Enter your local rate as a custom percentage and ignore the CGST/SGST split, which is specific to India's dual-GST structure.

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