How to Calculate GST, CGST and SGST — Simple Guide (2026)
Whether you run a small business, freelance, or just want to understand the tax breakdown on your invoices, knowing how GST works is essential. This guide explains the difference between CGST, SGST, and IGST, walks through the common tax slabs, and shows you how to add or remove GST from any price.
CGST vs SGST vs IGST — What Is the Difference?
- CGST (Central GST) — The portion of GST collected by the Central Government. Applied on transactions within the same state.
- SGST (State GST) — The portion collected by the State Government. Also applied on intra-state transactions. CGST and SGST are always equal.
- IGST (Integrated GST) — Applied on inter-state transactions (seller in one state, buyer in another). IGST equals CGST + SGST combined. The Central Government later distributes the state portion to the destination state.
For example, if you buy a product worth Rs 1,000 with 18% GST within your state, you pay 9% CGST (Rs 90) + 9% SGST (Rs 90) = Rs 180 total GST. If the same product is bought from another state, you pay 18% IGST (Rs 180) instead.
Common GST Slabs in India
| GST Rate | CGST + SGST Split | Examples |
|---|---|---|
| 5% | 2.5% + 2.5% | Packaged food, economy hotel rooms, transport |
| 12% | 6% + 6% | Processed food, business class air tickets, apparel above Rs 1,000 |
| 18% | 9% + 9% | Most services, electronics, restaurants with AC, IT services |
| 28% | 14% + 14% | Luxury items, automobiles, aerated drinks, cement |
Essential items like fresh vegetables, milk, and unbranded grains attract 0% GST. Some items also carry an additional cess on top of the 28% slab (like certain cars and tobacco products).
How to Add GST to a Price
To calculate the GST-inclusive price from a base price:
Final Price = Base Price + GST Amount
Example: A product costs Rs 5,000 before tax. GST rate is 18%. GST amount = 5,000 x 18/100 = Rs 900. Final price = Rs 5,900. On the invoice, this splits as Rs 450 CGST + Rs 450 SGST (for intra-state sales).
How to Remove GST from a Price
When you have the GST-inclusive price and want to find the base price:
Example: A bill shows Rs 5,900 inclusive of 18% GST. Base price = 5,900 x 100 / 118 = Rs 5,000. GST paid = Rs 900. This reverse calculation is useful when checking if a vendor has charged the correct tax amount.
Use Toolkiya GST Calculator
Instead of calculating manually every time, use the Toolkiya GST Calculator. Enter the amount, select the GST slab, and instantly see the tax breakdown with CGST, SGST, and IGST amounts. The tool handles both adding GST to a base price and extracting GST from an inclusive price. It works on mobile too, making it handy for quick calculations while creating invoices or checking bills. You might also find our EMI calculation guide useful if you are planning a business loan.
Quick Tips for Business Owners
- Always mention the HSN/SAC code on invoices to identify the applicable GST rate.
- File GST returns on time to avoid late fees (Rs 50/day for GSTR-3B, Rs 20/day for nil returns).
- Claim Input Tax Credit (ITC) on business purchases to reduce your net GST liability.
- Keep digital copies of all invoices for at least 6 years as per GST audit requirements.
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