What is GST?
Goods and Services Tax (GST) is a unified indirect tax that replaced VAT, service tax, excise duty, and several other taxes in India from July 1, 2017. It is levied on the supply of goods and services at each stage of the supply chain.
GST in India has four main rates: 5%, 12%, 18%, and 28%, plus a nil rate (0%) for essential goods.
The Three Types of GST
Understanding which GST type applies depends on whether the transaction is intra-state or inter-state:
| Type | Full Form | Who Collects | When |
|---|---|---|---|
| CGST | Central GST | Central Government | Intra-state (within same state) |
| SGST | State GST | State Government | Intra-state (within same state) |
| IGST | Integrated GST | Central Government | Inter-state (across states) |
Example: If you sell goods in Maharashtra to a Maharashtra customer, you charge CGST (half rate) + SGST (half rate). If you sell to a customer in Delhi, you charge IGST (full rate).
GST Calculation Formula
1. Adding GST to a Base Price (Exclusive GST)
GST Amount = Base Price × GST Rate / 100 Final Price = Base Price + GST Amount
Example: Base price ₹10,000, GST rate 18%
- GST = 10,000 × 18/100 = ₹1,800
- Final price = 10,000 + 1,800 = ₹11,800
CGST = ₹900 (9%), SGST = ₹900 (9%) for intra-state
2. Removing GST from Total (Inclusive / Reverse GST)
Base Price = Total Price / (1 + GST Rate/100) GST Amount = Total Price – Base Price
Example: Total price ₹11,800, GST rate 18%
- Base price = 11,800 / (1 + 18/100) = 11,800 / 1.18 = ₹10,000
- GST amount = 11,800 – 10,000 = ₹1,800
This is reverse GST calculation — useful when you see an MRP that already includes GST and need to find the base price.
GST Rate for Common Goods and Services
| Category | GST Rate |
|---|---|
| Essential food items (rice, wheat, milk) | 0% |
| Sugar, edible oils, packed food | 5% |
| Butter, cheese, ghee, packed dried fruits | 12% |
| Most services (financial, telecom, restaurants) | 18% |
| Luxury goods (cars >₹10L, tobacco, aerated drinks) | 28% |
| Cement, paint, washing machines | 28% |
CGST and SGST: How the Split Works
For intra-state transactions, the GST rate is split equally:
- 18% GST = 9% CGST + 9% SGST
- 12% GST = 6% CGST + 6% SGST
- 5% GST = 2.5% CGST + 2.5% SGST
- 28% GST = 14% CGST + 14% SGST
For inter-state, the full rate goes as IGST:
- 18% GST = 18% IGST (no split)
IGST for Inter-State Transactions
IGST is charged on transactions between different states or on imports. The rate is the same as the combined GST rate. The input tax credit (ITC) on IGST can be used to offset CGST or SGST liability later.
Common Mistakes When Calculating GST
Mistake 1: Applying GST on GST-inclusive price If ₹11,800 is the final price (GST inclusive), don't calculate 18% of ₹11,800. First extract the base price using reverse GST, then verify.
Mistake 2: Confusing IGST and CGST+SGST If your customer is in the same state, always use CGST+SGST. Using IGST for intra-state transactions is a compliance error.
Mistake 3: Wrong rate for mixed supplies When selling a bundle of items with different GST rates, each component must be taxed at its applicable rate, not a single blended rate.
Try the Calculator
Don't want to do the math manually? Use our free GST Calculator to instantly compute GST inclusive, exclusive, and reverse calculations for all slabs — with CGST and SGST breakdown.
Also see our Discount Calculator if you need to calculate discounts before or after GST.