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Understanding GST in India: Slab Rates and Tax Calculations

ConverterPilot Tax Editorial May 16, 2026 5 min read

Introduced on July 1, 2017, the Goods and Services Tax (GST) replaced a complex web of indirect taxes in India (such as VAT, service tax, and excise duty) with a unified tax structure. Understanding how GST is classified and calculated is essential for business owners, consumers, and freelancers.

The Structure of GST: CGST, SGST, and IGST

Because India has a federal system of government, GST is divided depending on where the transaction occurs:

  • CGST (Central GST): Collected by the Central Government on intra-state sales.
  • SGST (State GST): Collected by the State Government on intra-state sales.
  • IGST (Integrated GST): Collected by the Central Government on inter-state sales (between two different states) and imports.

For example, if you buy a laptop in Mumbai from a dealer in Pune, it is an intra-state transaction. If the GST rate is 18%, it will be split equally as 9% CGST and 9% SGST. If the laptop was shipped from Delhi, it would be an inter-state sale, and a single 18% IGST would apply.

GST Slab Rates in India

Goods and services are categorized under five primary tax slabs:

  • 0% (Exempt): Essential goods like fresh vegetables, milk, grains, and basic healthcare.
  • 5%: Common goods like sugar, tea, domestic LPG, and economy air travel.
  • 12%: Items like butter, cheese, computers, mobile phones, and business class air travel.
  • 18%: Most services, capital goods, hair oil, toothpaste, and restaurants.
  • 28%: Luxury and demerit goods like cars, tobacco, cement, and aerated drinks.

The Formulas for GST Calculation

Whether you are setting prices or checking invoices, you must know how to add GST to a base price or extract the base price from a GST-inclusive price.

1. Adding GST to Base Price

To find the final price after adding tax:

  • GST Amount = (Base Price * GST Rate) / 100
  • Total Cost = Base Price + GST Amount

2. Removing GST (GST-Inclusive Price)

To find the base price and the tax component already hidden inside a price tag:

  • Base Price = Inclusive Price / (1 + (GST Rate / 100))
  • GST Amount = Inclusive Price - Base Price

Worked Example: 18% GST on a Service Fee

Suppose you hire a consultant who quotes ₹10,000 (Base Price).

  • GST Amount: (₹10,000 * 18) / 100 = ₹1,800
  • Total Billing Cost: ₹10,000 + ₹1,800 = ₹11,800

Now, if a consumer pays a total bill of ₹11,800 (Inclusive Price) and you want to extract the central and state taxes:

  • Base Price: ₹11,800 / (1 + 0.18) = ₹10,000
  • Total GST: ₹11,800 - ₹10,000 = ₹1,800
  • CGST (9%): ₹900
  • SGST (9%): ₹900