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Free GST tool

GST calculator for India

Add or remove GST at 5%, 12%, 18% or 28% and see the CGST, SGST and IGST split instantly. Free, no sign-up, and nothing leaves your browser.

₹
GST rate
%
Calculation
Supply type
Base amount₹ 1,000.00
CGST (9%)₹ 90.00
SGST (9%)₹ 90.00
Total GST₹ 180.00
Total payable₹ 1,180.00

How this GST calculator works

GST (Goods and Services Tax) in India is charged as a percentage of the sale value. This calculator supports both directions:

  • Add GST — you enter the price before tax and it adds GST on top. Use this when quoting a customer or pricing a product.
  • Remove GST — you enter a GST-inclusive total and it works backwards to the base value and the tax inside it (reverse GST). Use this when a price already includes GST.

CGST, SGST and IGST

For a sale within the same state, GST is split equally into CGST (collected by the centre) and SGST (collected by the state). For a sale to another state, a single IGST applies at the full rate. The total tax is identical — only the split changes.

GST rate slabs

India uses five main GST slabs: 0%, 5%, 12%, 18% and 28%. Most goods and services sit at 12% or 18%. Use the HSN code finder to confirm the exact slab for a product, or read the GST rates & slabs guide.

Frequently asked questions

How is GST calculated on an amount?
To add GST, multiply the base amount by the GST rate and divide by 100, then add it back: GST = amount × rate ÷ 100. For example, ₹1,000 at 18% GST is ₹180 GST, so the total is ₹1,180. For intra-state sales this splits into 9% CGST (₹90) and 9% SGST (₹90); for inter-state sales it is a single 18% IGST (₹180).
How do I remove GST from a total (reverse GST)?
Use the "Remove GST" mode. To find the base amount from a GST-inclusive total, divide the total by (1 + rate ÷ 100). For ₹1,180 inclusive of 18% GST, the base is 1180 ÷ 1.18 = ₹1,000 and the GST is ₹180.
What is the difference between CGST, SGST and IGST?
For a sale within the same state (intra-state), GST is split equally into CGST (central) and SGST (state). For a sale between two different states (inter-state), a single IGST is charged at the full rate. The total tax is the same either way — only the split differs.
What are the GST rate slabs in India?
The main GST slabs are 0%, 5%, 12%, 18% and 28%. Essential items are 0% or 5%, most goods and services are 12% or 18%, and luxury or sin goods are 28%. Pick the slab that applies to your product or service.
Is this GST calculator free to use?
Yes. The BillRaja GST calculator is completely free, works in your browser with no sign-up, and never stores your numbers. For automatic GST on every bill, HSN-wise GST reports and GSTR-ready summaries, use the free BillRaja app.

Related tools & guides

GST invoice generator

Create a GST-ready invoice PDF free.

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GST invoice format

Download GST invoice templates in Excel, Word & PDF.

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HSN code finder

Find the HSN code and GST rate for any product.

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GST rates & slabs guide

Which goods fall in 5/12/18/28%.

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