How to use the GST Calculator
- 1
Choose Add GST if your price is before tax, or Remove GST if the amount already includes tax.
- 2
Type the amount in rupees.
- 3
Tap a GST rate, or type your own in the custom rate box. Use the old 12% or 28% buttons only for invoices dated before 22 September 2025.
- 4
Pick Within state for a CGST + SGST split, or Other state for IGST.
- 5
Read the net amount, GST and total, then copy the breakdown for your invoice or records.
Two formulas: adding GST and taking it out
Adding GST is the easy direction. Multiply the taxable value by the rate and add the result. A ₹10,000 service at 18% carries ₹10,000 × 18 ÷ 100 = ₹1,800 of GST, so the invoice total is ₹11,800.
Removing GST needs a different formula, because the tax was calculated on a smaller number than the one you are holding. The base price is the inclusive amount × 100 ÷ (100 + rate). For a bill of ₹1,180 at 18%, that is 1,180 × 100 ÷ 118 = ₹1,000, and the GST inside it is ₹180. At 5%, a ₹1,050 bill breaks down into ₹1,000 plus ₹50 of tax.
The mistake most people make when removing GST
It is common to see someone take 18% of the inclusive price and subtract it. On ₹1,180 that gives a GST of ₹212.40 and a base price of ₹967.60, which is wrong by more than ₹32. The error grows with the amount and the rate. On a ₹5 lakh bill at 18% the shortcut overstates GST by about ₹13,700.
The reason is simple: 18% of ₹1,000 is ₹180, but 18% of ₹1,180 is a bigger number. Always divide by (100 + rate), which is what the Remove GST mode does. If you deal in reverse calculations often, remember these divisors: 1.05 for 5%, 1.18 for 18% and 1.40 for 40%.
CGST, SGST or IGST: which one goes on the invoice
The total tax does not change with the type of supply. Only the way it is labelled and shared between the Centre and the states changes.
- Intra-state supply (seller and place of supply in the same state): charge CGST and SGST, each at half the rate. On ₹10,000 at 18% that is CGST 9% = ₹900 and SGST 9% = ₹900.
- Inter-state supply (place of supply in another state), and imports: charge IGST at the full rate, so ₹1,800 at 18%.
- Union territories without their own legislature, such as Chandigarh or Ladakh, use UTGST in place of SGST. The split is still half and half.
Getting this wrong is not just cosmetic. If you charge CGST + SGST on what was really an inter-state sale, you generally have to pay IGST and then claim a refund of the wrongly paid tax, which takes time. Decide the place of supply first, then use the toggle above.
GST 2.0 rates from 22 September 2025
The GST Council's rate rationalisation, often called GST 2.0, came into effect on 22 September 2025. The old four-slab structure of 5%, 12%, 18% and 28% gave way to two main slabs and a higher rate for luxury and sin goods. A few examples where the change was widely notified:
| Rate | Used for | Examples |
|---|---|---|
| Nil | Exempt goods and services | Individual life and health insurance premiums, UHT milk, paneer, roti and paratha |
| 5% | Merit and everyday items | Toothpaste, soap, shampoo, butter, ghee, many packaged foods |
| 18% | Standard rate for most goods and services | Most services, ACs, TVs, cement, small cars, motorcycles up to 350 cc |
| 40% | Luxury and sin goods | Aerated and sugary drinks, mid-size and large cars, motorcycles above 350 cc, yachts |
| 3% | Special rate | Gold, silver and jewellery |
| 0.25% | Special rate | Rough diamonds |
Rates are tied to the HSN code for goods and the SAC code for services, and some items carry conditions or exceptions. Always confirm the rate for your exact code on the CBIC rate notifications or with your accountant before you bill a customer.
When the old 12% and 28% rates still matter
Rates apply according to the time of supply, so invoices dated before 22 September 2025 keep the rate that applied then. You might need the old figures to check a purchase bill from mid-2025, file an amendment, settle a dispute about an old order, or reconcile input tax credit for that period. That is why the calculator keeps 12% and 28% as separate buttons, apart from the current rates.
If you sell, update your billing software and printed price lists to the new rates. Charging 12% today on something that now sits at 5% means overcharging your customer, and the excess still has to be paid to the government.
What the calculator does not decide for you
It does the arithmetic. It does not tell you whether an item is taxable, which HSN code fits, whether reverse charge applies, or whether you can claim input tax credit. Compensation cess on some goods is also outside its scope. For a valid tax invoice you still need your GSTIN, the buyer's details where required, the HSN or SAC code, the taxable value and each tax shown separately. Use the copied breakdown as a quick check, not as a substitute for proper GST advice.
Frequently asked questions
How do I calculate GST from a total amount?
Divide the total by (1 + rate ÷ 100) to get the price before tax, then subtract that from the total to get the GST. For ₹1,180 at 18%, 1,180 ÷ 1.18 = ₹1,000, so the GST is ₹180. Select Remove GST above to do this automatically.
What are the GST rates in India now?
Since 22 September 2025 the main slabs are 5% and 18%, with 40% for luxury and sin goods. Special rates of 3% for gold and silver and 0.25% for rough diamonds continue, and many essentials are exempt.
Are 12% and 28% GST rates gone?
For most goods and services they were removed under GST 2.0, with items moved mainly to 5%, 18% or 40%. You still need them to check invoices issued before the change.
What is the difference between CGST, SGST and IGST?
CGST goes to the Centre and SGST to the state, and both apply on sales within one state at half the rate each. IGST applies on sales between states and on imports, at the full rate. The customer pays the same total either way.
Is GST charged on the discounted price?
Yes, if the discount is shown on the invoice at the time of sale, GST is calculated on the price after the discount. Enter the discounted price in Add GST mode.
Can I use a custom GST rate?
Yes. Type any rate in the custom rate box and the calculator uses it instead of the buttons. Clear the box to go back to the standard rates.
Last updated on November 9, 2026