How to use: GST calculator
- 1Enter the amount in rupees.
- 2Pick the GST rate, or type a custom rate.
- 3Choose whether the amount is before GST (add GST) or already includes GST (remove GST).
- 4Choose same state for CGST + SGST, or other state for IGST. The result updates as you type.
GST formulas
Adding GST (exclusive amount)
- GST = Amount × Rate ÷ 100
- Total = Amount + GST
Removing GST (inclusive amount)
- Base amount = Total × 100 ÷ (100 + Rate)
- GST = Total − Base amount
Worked example
You sell goods worth ₹25,000 to a customer in the same state at 18% GST.
| Item | Amount |
|---|---|
| Taxable value | ₹25,000.00 |
| CGST @ 9% | ₹2,250.00 |
| SGST @ 9% | ₹2,250.00 |
| Invoice total | ₹29,500.00 |
If the customer were in another state, the invoice would show a single IGST line of ₹4,500 instead of CGST and SGST.
Use it for quotes and invoices
Freelancers and small businesses often quote an “all-inclusive” price and need to know the taxable value for the invoice. Enter the inclusive price, choose “Including GST” and the calculator gives you the exact taxable value and tax to print.
This calculator is for quick estimates. For filing returns, follow your accountant’s advice and the official GST rate notifications.
Frequently asked questions
How do I calculate GST on an amount?
Multiply the amount by the GST rate and divide by 100. For ₹1,000 at 18%, GST is ₹180 and the total is ₹1,180.
How do I remove GST from a total (GST inclusive)?
Divide the total by (1 + rate/100). For ₹1,180 including 18% GST, the base amount is 1180 ÷ 1.18 = ₹1,000 and the GST is ₹180.
When is it CGST + SGST and when is it IGST?
For a sale within the same state, GST is split equally into CGST (central) and SGST (state). For a sale to another state, the full GST is charged as IGST.
Which GST rates apply in India?
The main slabs are 5% and 18%, with 40% for luxury and sin goods, plus special rates such as 0.25% and 3% for certain items. Older invoices may show the earlier 12% and 28% slabs. Always confirm the rate for your HSN or SAC code.
How accurate is the calculator?
Calculations are done in whole paise, so there are no floating-point rounding errors. CGST and SGST always add up exactly to the total GST.