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What is GST?
Goods and Services Tax (GST) is India's unified indirect tax that replaced VAT, service tax, excise duty, and a host of other cascading state and central levies. Rolled out on 1 July 2017, GST is charged on the supply of goods and services and is currently levied under four main slabs — 5%, 12%, 18%, and 28% — with a 0% (nil-rated) category for essentials. This calculator lets you either add GST to a base price or remove GST from a price that already includes tax, and shows the CGST/SGST split for the transaction.
How the Calculation Works
The tool behaves differently depending on whether your entered amount already includes GST:
GST Amount = Amount × Rate ÷ 100
Total Price = Amount + GST Amount
Remove GST (GST-Inclusive amount):
Original Price = Total × 100 ÷ (100 + Rate)
GST Amount = Total − Original Price
Split (intra-state): CGST = GST Amount ÷ 2, SGST = GST Amount ÷ 2
Worked Example 1 — Adding GST
A wholesaler sells goods worth ₹10,000 (exclusive of tax) at the 18% slab:
- GST Amount = 10,000 × 18 ÷ 100 = ₹1,800
- Total Invoice Value = 10,000 + 1,800 = ₹11,800
- If sold within the same state: CGST = ₹900 and SGST = ₹900 (9% each)
Worked Example 2 — Removing GST (Reverse Calculation)
A retailer receives an invoice showing a final price of ₹23,600, which already includes 18% GST, and needs to know the original (pre-tax) value:
- Original Price = 23,600 × 100 ÷ 118 = ₹20,000
- GST Amount = 23,600 − 20,000 = ₹3,600
- CGST = ₹1,800 and SGST = ₹1,800 for an intra-state sale
GST Slabs in India
| Slab | Typical Items |
|---|---|
| 0% | Fresh milk, eggs, fresh produce, unbranded food grains, printed books |
| 5% | Packaged food staples, footwear under ₹1,000, economy transport, life-saving drugs |
| 12% | Processed food, business-class air tickets, some mobile phones, ayurvedic medicines |
| 18% | Most services, electronics, software/SaaS, AC restaurants, financial services |
| 28% | Luxury cars, tobacco, aerated drinks, high-end consumer durables |
CGST, SGST, and IGST — What's the Difference?
When goods or services are sold within the same state, GST is split equally between CGST (Central GST, goes to the union government) and SGST (State GST, goes to the state government) — each at half the total rate, as shown in the examples above. When a sale crosses state lines, the full rate is instead charged as a single IGST (Integrated GST), which is later apportioned between the centre and the destination state. Our calculator always shows the CGST/SGST breakdown, which applies for intra-state billing; for an inter-state invoice, the same total GST amount would appear entirely as IGST instead.
How to Use This GST Calculator
- Enter the amount — either the base (pre-tax) price or a total that already includes GST.
- Select the applicable GST rate: 5%, 12%, 18%, or 28%.
- Choose GST Exclusive if you want to add tax, or GST Inclusive if you want to extract the tax already built into the price.
- Click Calculate to instantly view the GST amount, CGST, SGST, and the final/original price.
Working out a plain percentage rather than a tax slab? Try the Percentage Calculator. Calculating a sale discount before tax is added? See the Discount Calculator.
Common GST Mistakes to Avoid
Many small business owners and freelancers get their GST calculations wrong in predictable ways. The most common error is applying the wrong slab — treating a 12% item as 18%, for instance — which can lead to short or excess tax collection and mismatches during GSTR-1/GSTR-3B filing. Another frequent mistake is confusing GST-inclusive and GST-exclusive amounts: quoting a price as "₹1,000 plus GST" versus "₹1,000 including GST" produces very different final bills, so always clarify which one you mean before invoicing. Businesses also sometimes forget that supplies to another state attract IGST, not CGST+SGST — charging the wrong tax type can invalidate the buyer's input tax credit claim. Finally, composition scheme dealers (turnover under ₹1.5 crore, or ₹75 lakh in special category states) must not charge GST separately on invoices at all, since they pay tax out of their own margin instead.
Frequently Asked Questions
Q: Is the GST shown on a shop receipt already included in the MRP?
A: Yes. Under India's MRP rules, the Maximum Retail Price printed on a packaged product is inclusive of all taxes, including GST. If you want to know how much of that final MRP is tax, use the "GST Inclusive" mode on this calculator to reverse-calculate the base price and the GST portion.
Q: What's the difference between CGST+SGST and IGST on a bill?
A: CGST and SGST apply when the buyer and seller are in the same state — the total GST is split equally between the central and state governments (e.g., 9%+9% for an 18% rate). IGST applies for inter-state transactions and is a single combined rate collected by the central government, later apportioned to the destination state.
Q: Does a small business or freelancer always need to charge GST?
A: Not necessarily. GST registration is mandatory only once your aggregate turnover crosses ₹40 lakh for goods (₹20 lakh in special category states) or ₹20 lakh for services (₹10 lakh in special category states) in a financial year. Below this threshold, you are not required to register or charge GST, though voluntary registration is allowed.
Q: What GST rate applies to restaurant bills?
A: Most standalone restaurants (non-AC or AC, without liquor licence) charge 5% GST without input tax credit. Restaurants inside 5-star or similar-rated hotels, or those charging room tariffs above ₹7,500, may fall under the 18% slab with input tax credit. Always check the rate printed on your specific bill, as rules for hotel-linked restaurants differ from standalone ones.
Q: Can GST rates change, and how do I stay updated?
A: Yes, the GST Council revises rates periodically based on recommendations from state and central finance ministers. This calculator's slabs (5%, 12%, 18%, 28%) reflect the rates as of publication, but always verify the latest applicable rate for your specific goods or services on the official GST portal (gst.gov.in) before filing returns.
GST for Freelancers and E-commerce Sellers
Freelancers and online sellers registered under GST need to charge the applicable slab rate on their invoices once their turnover crosses the registration threshold, and e-commerce operators like Amazon or Flipkart typically deduct Tax Collected at Source (TCS) at 1% on the net taxable supply value before remitting the balance to sellers. This TCS is separate from the GST charged on the invoice itself and can be claimed as a credit against a seller's GST liability while filing returns, so it's not an additional cost but does affect short-term cash flow for sellers relying on marketplace payouts.
📅 Last reviewed: July 2026 · Formulas verified against RBI/SEBI/IT Dept guidelines.