GST Calculator India: How to Calculate CGST, SGST & IGST on Any Product

India's GST system has four rate slabs, three tax components, and one formula — and most people only understand the formula after their first wrong invoice.

Goods and Services Tax (GST) replaced 17 different indirect taxes in India on July 1, 2017. The intent was simplification, but the three-component structure — CGST, SGST, and IGST — still confuses businesses, especially around interstate vs intrastate transactions. Whether you are raising an invoice, calculating your input tax credit, or pricing a product, understanding this structure is non-negotiable.

Use the free WOWHOW GST calculator for instant calculations. This guide explains the logic behind the numbers.

Try it yourself: Free GST 2.0 Rate Finder (old vs new rates) — free, no signup, runs in your browser.

The Four GST Rate Slabs

GST in India applies at four primary rates, determined by the product or service's HSN code (for goods) or SAC code (for services):

• 5%: Essential goods — edible oils, sugar, tea, coffee (not instant), processed food, household necessities
• 12%: Standard goods — butter, ghee, cheese, frozen meat, fruit juice, ayurvedic medicines, mobile phones
• 18%: Most goods and services — restaurants (air-conditioned), financial services, IT services, telecom, most manufactured goods
• 28%: Luxury and demerit goods — automobiles, tobacco, aerated beverages, luxury hotels, gambling

A zero-rate (0%) category covers exempt supplies — fresh vegetables, milk, eggs, bread, salt, educational services. These are completely outside the GST net.

CGST, SGST, and IGST: What Each Component Means

The GST rate you see on an invoice (e.g., 18%) is split into components depending on whether the transaction is intrastate or interstate.

Intrastate Supply (CGST + SGST)

When a supplier and buyer are in the same state, the GST is split equally between the Central Government (CGST) and the State Government (SGST):

• 18% GST on an intrastate transaction = 9% CGST + 9% SGST
• 12% GST = 6% CGST + 6% SGST
• 5% GST = 2.5% CGST + 2.5% SGST

Both components are charged on the same taxable value. They appear as separate line items on the invoice. The buyer pays both, and the supplier remits CGST to the Centre and SGST to the state exchequer through their GST filings.

Interstate Supply (IGST)

When the supplier and buyer are in different states, only IGST (Integrated GST) is charged — at the full applicable rate:

• 18% GST on an interstate transaction = 18% IGST (no split)
• 12% GST = 12% IGST

IGST is collected by the Centre and subsequently apportioned between the origin state, destination state, and Centre according to the IGST Act's settlement mechanism. From the supplier's and buyer's perspective, it is simply one number at the full rate.

Union Territory GST (UTGST)

Transactions within a Union Territory (Delhi, Chandigarh, Puducherry, etc.) use UTGST instead of SGST. The mechanics are identical to SGST — CGST + UTGST = full applicable rate for intrastate UT transactions.

GST Calculation Formula

The calculation logic is simple:

Exclusive GST (Adding GST to a base price)

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

Example: Product priced at ₹1,000, GST rate 18% (intrastate)
CGST = ₹1,000 × 9% = ₹90
SGST = ₹1,000 × 9% = ₹90
Total Invoice Value = ₹1,000 + ₹90 + ₹90 = ₹1,180

Inclusive GST (Extracting GST from a GST-inclusive price)

Taxable Value = GST-Inclusive Price / (1 + GST Rate/100)
GST Amount = GST-Inclusive Price - Taxable Value

Example: Product MRP ₹1,180 (inclusive of 18% GST)
Taxable Value = ₹1,180 / 1.18 = ₹1,000
GST Amount = ₹1,180 − ₹1,000 = ₹180 (₹90 CGST + ₹90 SGST)

The GST calculator handles both exclusive and inclusive calculations for all four rate slabs with CGST/SGST/IGST breakdown.

Input Tax Credit (ITC): How GST Offset Works

Input Tax Credit is the mechanism that prevents tax cascading — a registered business can offset the GST it paid on purchases (input tax) against the GST it collects from customers (output tax). Only the net amount is remitted to the government.

ITC rules for 2025-26:

• CGST input credit can be used against CGST and IGST output liability (in that order)
• SGST input credit can be used against SGST and IGST output liability (in that order)
• IGST input credit can be used against IGST, CGST, and SGST output liability (in that order)
• CGST credit cannot be used against SGST liability and vice versa

Example: A manufacturer in Maharashtra pays ₹18,000 IGST on raw materials purchased from a Rajasthan supplier. On finished goods sold to customers in Maharashtra, they collect ₹9,000 CGST + ₹9,000 SGST. They can set off the ₹18,000 IGST credit against the ₹9,000 CGST and then ₹9,000 SGST liability — net tax payable is zero.

GST on Services: Key Rates for Freelancers and Agencies

Services have GST rates defined by SAC (Services Accounting Code):

• IT/software services: 18%
• Digital advertising services: 18%
• Professional services (consulting, legal, CA): 18%
• Freelance design/development: 18%
• Educational services (private institutes): 18%
• Restaurant (non-AC): 5% (no ITC)
• Hotel accommodation above ₹7,500/night: 18%

Freelancers with annual turnover above ₹20 lakh (₹10 lakh for special category states) are required to register for GST. Exports of services are zero-rated — you can claim ITC refunds on inputs used for exported services.

People Also Ask

What is the difference between CGST and SGST?

CGST (Central Goods and Services Tax) is collected by the Central Government. SGST (State Goods and Services Tax) is collected by the state government. They apply simultaneously on intrastate (within-state) transactions, each at half the applicable GST rate. On a 18% GST transaction within Maharashtra, 9% CGST goes to the Centre and 9% SGST goes to Maharashtra.

When does IGST apply instead of CGST+SGST?

IGST (Integrated Goods and Services Tax) applies to interstate transactions — when the supplier's GSTIN state and the place of supply are different states. IGST is charged at the full applicable rate (not split). Imports are also subject to IGST at the port of entry.

Is GST charged on exports?

No. Exports are zero-rated under GST. No GST is charged on exported goods or services, and the exporter can claim a refund of ITC on inputs used for export. This is to make Indian exports globally competitive. Exporters must file LUT (Letter of Undertaking) or IGST refund claims to access this benefit.

How do I find the GST rate for a specific product?

Use the HSN code lookup. The GST Council publishes rate schedules by HSN code. Most products have a 4-digit or 8-digit HSN code that maps to a GST rate. The CBIC GST rate search portal allows lookup by HSN code or product description. Browse the WOWHOW tools directory for financial calculators including GST tools.