GST calculator with CGST, SGST and IGST split
Add or remove GST at any slab, on one amount or on a full invoice of line items. The rate-wise tax summary below is the same breakup a GST tax invoice has to carry, so you can copy it straight onto a bill.
Slabs current for 2026 · runs entirely in your browser, nothing is sent to a server
What are you calculating?
Pick whether your amount already includes GST, and whether the supply crosses a state border.
Amount
Enter the value before GST.
The everyday slabs are 0, 5, 18 and 40 percent. 3% is the special rate for gold, silver and jewellery. 12% survives only for building bricks, fly ash blocks and earthen roofing tiles — it was withdrawn for everything else on 22 September 2025.
Not sure which rate applies? Look it up by product or HSN code.
Invoice lines
Add each line with its own rate. Useful when one bill mixes rates — a 5% item and an 18% item on the same invoice.
Tax summary
Rate-wise summary
A tax invoice must show tax grouped by rate. This is that breakup.
| Rate | Taxable | Tax |
|---|
Figures are rounded to two decimals per line, the way an invoice is.
How GST is calculated
Adding GST is a percentage on top of the taxable value. Removing it is the harder direction, and it is where most manual calculations go wrong.
Adding GST. Multiply the taxable value by the rate. At 18% on ₹10,000 the GST is ₹1,800 and the invoice total is ₹11,800.
Removing GST. Divide the inclusive total by 1 plus the rate as a decimal — not by the rate. At 18%, divide ₹11,800 by 1.18 to get ₹10,000 of taxable value, and the difference of ₹1,800 is the tax. Taking 18% of ₹11,800 gives ₹2,124, which is wrong by ₹324.
CGST, SGST and IGST
The total tax is the same either way. Only the split changes, and it is decided by the place of supply rather than by where either party is registered.
- Intra-state — supplier and place of supply in the same state. The rate splits equally: 18% becomes 9% CGST and 9% SGST.
- Inter-state — different states, or an export or SEZ supply. A single IGST applies at the full 18%.
Getting this wrong is expensive in practice. Tax paid under the wrong head cannot simply be reallocated; you claim a refund of the wrong one and pay the right one, and Section 77 of the CGST Act read with Section 19 of the IGST Act protects you from interest where the mistake was genuine.
The rounding rule
Section 170 of the CGST Act says tax should be rounded to the nearest rupee. In practice most accounting software carries two decimals per line and rounds the invoice total, which is what this calculator does. Small differences between your books and a supplier's invoice usually trace back to whether rounding happened per line or once at the end.
What the taxable value includes
The value GST applies to is more than the bare price of the goods. Under Section 15 it includes packing, commission, and any freight or installation the supplier bills on the same invoice. It excludes a discount shown on the face of the invoice, which reduces the taxable value, but not a post-sale cashback, which does not.
Common questions
Divide the GST-inclusive total by 1 plus the rate as a decimal. At 18%, divide by 1.18. Do not take 18% of the inclusive amount — that overstates the tax by roughly 18%.
0%, 5%, 18% and 40%, after the September 2025 GST 2.0 reforms withdrew the 12% and 28% slabs. A special 3% applies to gold, silver and jewellery, and 12% survives only for building bricks, fly ash blocks and earthen roofing tiles.
When the supplier and the place of supply are in different states, and on exports and supplies to an SEZ. The total rate is identical; only the split differs.
Yes, and it is common. Each line carries its own rate and HSN or SAC code, and the invoice shows a rate-wise tax summary. Switch this calculator to Full invoice mode to build that summary.
No. The calculator runs entirely in your browser. Nothing is transmitted, logged or stored, and closing the tab discards it.