How the GST calculator works
Choose whether your amount is before GST (you want to add tax to a price) or including GST (you want to know how much tax is inside a bill). Pick the rate and whether the sale is within your state or to another state.
Removing GST: Amount before GST = Amount × 100 ÷ (100 + Rate)
CGST, SGST and IGST
For a sale within the same state, GST is split equally into CGST (central) and SGST (state) – or UTGST in union territories. For a sale to another state, the full amount is charged as IGST. The total tax is the same either way.
Which GST rate applies?
From 22 September 2025 most goods and services moved to two main slabs, 5% and 18%, with 40% for luxury and sin goods. Special rates such as 0.25% and 3% still apply to specific items like rough diamonds and gold. The 12% and 28% options are kept here for older invoices. Always check the rate for your HSN or SAC code.
Need help with invoices or returns? See our GST return filing and GST registration services.
Frequently Asked Questions
How do I calculate GST from a total amount?
Divide the total by (100 + rate) and multiply by 100 to get the amount before GST. The difference is the GST. For 18%, ₹11,800 contains ₹10,000 + ₹1,800 GST.
When is IGST charged instead of CGST and SGST?
IGST applies when the supplier and the place of supply are in different states, and on imports and exports. CGST and SGST apply to sales within the same state.
What are the current GST rates?
Since 22 September 2025 the main rates are 5% and 18%, with 40% on luxury and sin goods, plus special rates such as 0.25% and 3% for certain items. Some goods and services are exempt.
Can I round off GST on an invoice?
GST is calculated on each line, and the invoice total can be rounded to the nearest rupee.
This calculator gives an estimate based on the rules shown above. Rates and limits change through budgets and notifications – confirm with a professional before you file or pay.