GST Calculator for CGST, SGST & IGST
Add GST on top of an amount, or strip it out of a GST-inclusive price. See the base, tax split and total update as you type.
GST will be added on top of the amount you entered.
For inter-state sales, the same total GST is charged as a single IGST of ₹1,800.00 instead of CGST + SGST.
How GST is calculated in India
Goods and Services Tax replaced a tangle of older indirect taxes with a single, destination-based tax. What changes from one sale to the next is not the rate, but how the tax is split.
Intra-state: CGST + SGST
When buyer and seller are in the same state, the GST rate is split equally between Central GST and State GST. An 18% sale becomes 9% CGST plus 9% SGST — each half goes to a different government.
Inter-state: IGST
When the sale crosses a state border, the whole rate is charged as a single Integrated GST. The total tax is identical to CGST + SGST — it is just collected together and settled between states.
HSN decides the rate
Every product carries an HSN code (SAC for services). That code maps to one of the GST slabs — 0%, 3%, 5%, 18% or 40% — so getting the HSN right is what makes the tax on each line correct.
The maths
- Adding GST: GST = amount × rate ÷ 100; total = amount + GST.
- Removing GST: base = amount ÷ (1 + rate ÷ 100); GST = amount − base.
- Split: CGST = SGST = GST ÷ 2 within a state; IGST = full GST across states.
Keep going: rates, formats & billing
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GST calculator FAQ
To add GST, multiply the amount by the GST rate (e.g. 18% = amount × 0.18) and add it to the base. To remove GST from a GST-inclusive amount, divide by (1 + rate/100) to get the base, and the remainder is the GST. This calculator does both — just pick "GST-exclusive" to add or "GST-inclusive" to remove.