GST Calculator: 18% Rate
Add 18% GST to a base price or pull it out of an inclusive amount, with the CGST/SGST split and a ready reckoner for common amounts.
Add: amount is before tax · Remove: amount already includes GST
Decides CGST+SGST vs IGST split
18% GST ready reckoner
The 18% slab is the standard rate, covering most services and manufactured goods, and since the September 2025 rate revision also most items that were earlier at 28%. The calculator above is preset to 18%: type any amount and switch between adding GST to a base price and removing GST from an inclusive price.
| Amount (₹) | +18% GST adds (₹) | Invoice total (₹) | If ₹amount includes GST: base (₹) | GST inside (₹) |
|---|---|---|---|---|
| 1,000 | 180 | 1,180 | 847 | 153 |
| 5,000 | 900 | 5,900 | 4,237 | 763 |
| 10,000 | 1,800 | 11,800 | 8,475 | 1,525 |
| 25,000 | 4,500 | 29,500 | 21,186 | 3,814 |
| 50,000 | 9,000 | 59,000 | 42,373 | 7,627 |
| 1,00,000 | 18,000 | 1,18,000 | 84,746 | 15,254 |
CGST and SGST split at 18%
For a sale within one state, 18% GST is collected as 9% CGST (to the centre) plus 9% SGST (to the state). For an inter-state sale the full 18% is charged as IGST. The split changes who receives the tax, not what the customer pays: the invoice total is identical either way.
Removing GST from an inclusive price
To extract the base from a GST-inclusive amount, divide by 1.18. For example, ₹1,000 inclusive of 18% GST is ₹847.46 base plus ₹152.54 tax. Multiplying the inclusive amount by 18% instead is the classic mistake, and it always overstates the tax.
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Frequently asked questions
How do I calculate 18% GST on a price?
Multiply the base price by 0.18. On ₹10,000 that is ₹1,800 GST, for an invoice total of ₹11,800. The calculator above does this instantly, including the CGST/SGST split.
How do I remove 18% GST from an inclusive amount?
Divide the inclusive amount by 1.18. ₹10,000 inclusive of 18% GST is ₹8,474.58 base plus ₹1,525.42 GST.
What falls under the 18% GST slab?
It is the standard rate, covering most services and manufactured goods, and since the September 2025 rate revision also most items that were earlier at 28%. When in doubt, check the item’s current rate notification on cbic.gov.in, since rates are set per item, not per industry.
Is this calculator valid after the 2025 GST rate changes?
Yes. The September 2025 revision changed which items sit in which slab, but the arithmetic of adding or removing a given percentage is unchanged, and the calculator supports any custom rate including the special 40% rate.