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Free GST tool

GST calculator for India

Calculate CGST, SGST or IGST after verifying the rate for the exact item and supply date. Current principal, demerit, nil, special and historical calculations are supported.

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Calculate GST

Calculation
₹
GST rate
Effective 22 September 2025, the principal structure is 5% and 18%, with 40% for selected demerit supplies. Nil/exempt, special and historical rates still vary. Verify the item and date in the official notifications.
Supply type
Split equally: 9% CGST + 9% SGST
Total payable₹ 1,180.00

₹ 1,000.00 + 18% GST

Base amount₹ 1,000.00
CGST (9%)₹ 90.00
SGST (9%)₹ 90.00
Total GST₹ 180.00

How to calculate GST

  • Add GST — enter the price before tax to add GST on top (for pricing or quoting).
  • Remove GST — enter a GST-inclusive total to find the base value and the tax inside it (reverse GST).

CGST, SGST and IGST

Same-state sales split GST equally into CGST (centre) and SGST (state). Inter-state sales charge a single IGST at the full rate — the total tax is identical, only the split changes.

GST rates after 22 September 2025

The principal structure is a 5% merit rate and an 18% standard rate, with a 40% demerit rate for selected supplies. This headline structure does not replace the item-level rules: nil/exempt supplies, other notified or special rates and legacy transactions can still apply. The 0%, 12% and 28% buttons remain available for nil, historical or specially notified calculations; they are not a claim that those rates currently apply to a new sale.

See the GST rate reform guide for the verification workflow.

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?
From 22 September 2025, the principal GST structure is a 5% merit rate and an 18% standard rate, with a 40% demerit rate for selected supplies. Nil or exempt supplies, other notified or special rates, and legacy transactions still require item- and date-specific verification. A calculator preset does not determine the legally applicable rate.
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.

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HSN/SAC reference

Find a candidate code, then verify its current rate officially.

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GST rate reform guide

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Run it all in one app

Stop calculating GST by hand.

Save an officially verified HSN/SAC and rate in BillRaja, then apply its CGST/SGST or IGST split consistently on invoices. Free to start.

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