GST calculator
Add GST to an amount, or work backwards from a GST-inclusive total — with the CGST/SGST or IGST split worked out for you.
The amount you entered is the taxable value — GST is added to it. Within one state, GST splits into CGST and SGST.
Provided for quick reference and general guidance. Tax rules change and edge cases exist — confirm anything consequential with your CA or the GST portal before acting on it.
Adding GST vs removing it
These are two different sums, and mixing them up is the most common GST arithmetic error. If you have a taxable value and need the invoice total, GST is added on top: ₹10,000 at 18% becomes ₹11,800. If you have a total that already includes GST and need to know the taxable value, you cannot simply subtract 18% — you divide by 1.18. Taking 18% off ₹11,800 gives ₹9,676, which is wrong by ₹324.
The split depends on where the supply goes, not on the rate. Within a single state the tax divides equally into CGST and SGST (or UTGST in a union territory) — 18% becomes 9% + 9%. When the supply crosses a state boundary, the whole 18% is IGST instead. The total tax is identical either way; only the heads it sits under change.
One detail worth knowing: when an odd amount of tax is split in half, the two halves cannot both be exact. Finkitaabh stores money as integer paise and uses a largest-remainder split, so CGST and SGST always add back to exactly the total tax — no stray paise appearing in your books over thousands of invoices. This calculator does the same thing.
Frequently asked questions
How do I remove GST from an amount?
Divide the GST-inclusive total by (1 + rate). At 18%, divide by 1.18 to get the taxable value; the difference is the GST. Subtracting 18% from the total gives the wrong answer, because the 18% was calculated on the smaller taxable value, not on the total.
When is it CGST + SGST and when is it IGST?
It depends on the place of supply. If supplier and place of supply are in the same state, the tax splits equally into CGST and SGST (or UTGST). If they are in different states, the full rate is charged as IGST. The total tax is the same; only the heads differ.
What are the current GST rates?
The common slabs are 0%, 5%, 12%, 18% and 28%, with special rates of 0.25% and 3% used for items such as precious stones and gold. The rate that applies depends on the HSN or SAC code of what you are selling — check the classification for your goods or services.
Does this calculator handle cess?
No. Compensation cess applies to a limited set of goods such as tobacco, aerated drinks and certain motor vehicles, and is charged in addition to GST at item-specific rates. Add it separately where it applies.
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