How GST is Calculated — Inclusive, Exclusive, and the CGST/SGST Split

GST (Goods and Services Tax) replaced a dozen indirect taxes in India with a single unified system. Whether you’re a freelancer issuing invoices or a shopper checking if the MRP includes tax — understanding GST math is essential.

Two scenarios

GST Exclusive (adding tax): You know the base price, and need to add GST on top.

GST Amount = Base Price × (Rate / 100)
Total = Base Price + GST Amount

GST Inclusive (extracting tax): You know the total (MRP), and need to find the base price.

Base Price = Total / (1 + Rate/100)
GST Amount = Total − Base Price

Worked example

A ₹10,000 service at 18% GST:

Exclusive: GST = ₹10,000 × 0.18 = ₹1,800 → Total = ₹11,800
Inclusive: Base = ₹10,000 / 1.18 = ₹8,475 → GST = ₹1,525

CGST and SGST

For intra-state transactions (buyer and seller in same state), GST is split equally:

• CGST (Central) = GST / 2
• SGST (State) = GST / 2

For inter-state transactions, the full rate is charged as IGST.

So ₹1,800 GST on an intra-state sale = ₹900 CGST + ₹900 SGST.

GST slab rates in India

Rate	Applies to
0%	Essential food items, healthcare
5%	Basic necessities, economy travel
12%	Processed food, business class
18%	Most services, electronics
28%	Luxury goods, automobiles, sin goods

Common mistakes

• Applying GST on already-inclusive MRP (double taxation)
• Confusing IGST with CGST+SGST on invoices
• Not reverse-calculating base price for tax credit claims

Use the OurDailyCalc GST calculator for instant inclusive/exclusive conversion with CGST/SGST split.

TL;DR

• Exclusive: add rate% on top. Inclusive: divide by (1 + rate%)
• CGST + SGST for intra-state; IGST for inter-state
• Most services are 18%; luxury goods are 28%
• Always clarify if a quoted price includes or excludes GST