GST (Goods and Services Tax) replaced the complex maze of indirect taxes in India from July 2017. But calculating GST — especially knowing whether a price is GST-inclusive or GST-exclusive, and how to split it into CGST/SGST or IGST — trips up even experienced business owners. This guide makes it clear.

GST Rate Structure in India 2026

RateCategoryExamples
0%ExemptFresh vegetables, milk, eggs, education, healthcare
5%Essential goodsPackaged food, medicines, transport services
12%Standard goodsProcessed food, computers, smartphones
18%Standard servicesMost services, restaurants, professional services
28%Luxury/sin goodsCars, cigarettes, AC restaurants, aerated drinks

CGST vs SGST vs IGST — The Key Difference

GST is split between the Centre and States:

  • Intra-state supply (seller and buyer in same state): CGST (half) + SGST (half). E.g., 18% GST = 9% CGST + 9% SGST
  • Inter-state supply (seller and buyer in different states): IGST (full rate). E.g., 18% GST = 18% IGST (goes to Centre, then shared with destination state)
  • Imports: IGST applies on all imports

Adding GST to a Price (GST-Exclusive Calculation)

If you know the base price (without GST) and need the final price:

GST Amount = Base Price × GST Rate ÷ 100
Final Price = Base Price + GST Amount

Example: Base price ₹10,000 with 18% GST = GST of ₹1,800 = Final price ₹11,800

Removing GST from a Price (GST-Inclusive Calculation)

If you know the MRP (price inclusive of GST) and need the base price:

Base Price = MRP × 100 ÷ (100 + GST Rate)
GST Amount = MRP − Base Price

Example: MRP ₹11,800 with 18% GST = Base price ₹11,800 × 100 ÷ 118 = ₹10,000. GST = ₹1,800

Common mistake: Don't calculate GST as simply 18% of MRP when removing GST. ₹11,800 × 18% = ₹2,124 (wrong). The correct GST is ₹1,800. Use the formula above or our GST calculator for accurate results.

GST Registration Threshold 2026

  • Businesses supplying goods: GST registration mandatory if turnover exceeds ₹40 lakh/year
  • Businesses supplying services: Mandatory if turnover exceeds ₹20 lakh/year
  • Special category states (NE, hill states): ₹20L for goods, ₹10L for services
  • E-commerce sellers and inter-state suppliers: Mandatory regardless of turnover

Use our GST Calculator to add or remove GST instantly and get the CGST/SGST/IGST breakdown with one click.