How to use the GST Calculator
- Enter the amount in rupees.
- Pick the GST rate that applies to your goods or service, or choose Custom rate.
- Choose Without GST if the amount is the base price, or With GST if it already includes tax (for example an MRP).
- Press Calculate. You will see the base amount, the GST, the total, and how the GST splits into CGST, SGST and IGST.
GST formulas
Adding GST to a base price:
Total = Amount + GST
Removing GST from a price that already includes it:
GST = Total − Base
Worked examples
Add 18% GST to ₹10,000: GST = 10,000 × 18 ÷ 100 = ₹1,800, so the total is ₹11,800.
Remove 18% GST from ₹11,800: Base = 11,800 × 100 ÷ 118 = ₹10,000, and the GST inside it is ₹1,800.
How GST appears on an invoice
A tax invoice normally shows the taxable value first, then the tax, then the total. For a sale of ₹10,000 within one state at 18% GST it looks like this:
| Line | Rate | Amount |
|---|---|---|
| Taxable value | - | ₹10,000.00 |
| CGST | 9% | ₹900.00 |
| SGST | 9% | ₹900.00 |
| Invoice total | 18% | ₹11,800.00 |
For a sale to another state the same tax is shown as a single IGST line of ₹1,800 at 18%.
Common mistakes to avoid
- Treating an MRP as the base price. An MRP already includes tax, so use Remove GST to find the base.
- Using an old slab. The 12% and 28% slabs no longer apply from 22 September 2025, so older worksheets and templates may be out of date.
- Assuming one rate for everything. The rate depends on the item and its HSN or SAC code, not on the shop.
- Ignoring invoice discounts. A discount shown on the invoice at the time of supply generally reduces the taxable value. Confirm the treatment for your case with your accountant.
Frequently asked questions
What are the current GST rates in India?
The main slabs are 0%, 5%, 18% and 40%, with special rates of 3% for gold, silver and platinum and 0.25% for rough precious stones. The 12% and 28% slabs were removed with effect from 22 September 2025. Always check the rate for your exact product or service.
What is the difference between adding and removing GST?
Adding GST starts from the price before tax and works out the tax on top. Removing GST starts from a tax-inclusive price, such as an MRP, and works backwards to the base price and the tax inside it.
What are CGST, SGST and IGST?
For a sale within one state, the GST is split equally between the Centre (CGST) and the State (SGST). For a sale between states, the full rate is charged as IGST. The total tax is the same either way.
How do I calculate GST on an MRP?
An MRP already includes GST. Choose With GST (remove GST), enter the MRP and the rate, and the calculator gives the base price and the GST amount.
Can I use this for filing returns or invoices?
It is a quick helper for estimates and checking figures. For invoices and returns, confirm the HSN/SAC code and rate for your goods or services and consult a qualified accountant.
Is the price I see in a shop inclusive of GST?
For packaged goods sold to consumers the printed MRP is inclusive of all taxes, so the shopkeeper cannot add GST on top of it. Business-to-business quotes are often given without GST, so check which one you are looking at.
Which rate should I use if I am not sure?
Look up your product or service on the official GST rate finder or ask your accountant. Using a guessed rate can make invoices wrong.