Finance Guide

How to Calculate GST in India — Complete Guide with Examples

🧮 5 min read · Updated May 2026 · By ConvertMate Team

GST calculation is a daily necessity for millions of business owners, shopkeepers, freelancers, and accountants across India. Whether you need to add GST to a base price for an invoice, remove GST from an inclusive price to find the original amount, or understand how much CGST and SGST to show on an invoice — this guide covers it all with clear examples.

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GST Slabs in India — 2025

GST Rate	Common Examples
0% (Exempt)	Fresh vegetables, milk, eggs, rice, wheat, pulses, books, educational services
5%	Packaged food, footwear under ₹1000, transport, economy hotel rooms
12%	Butter, ghee, mobile phones, construction services, business class travel
18%	Most services (IT, consulting, freelance, banking), electronics, restaurants with AC
28%	Luxury cars, tobacco, aerated drinks, 5-star hotels, casinos

How to Add GST to a Price (GST Exclusive Calculation)

Use this when you know the base price (without GST) and need to find the total amount including GST.

Formula: GST Amount = Base Price × (GST Rate ÷ 100)
Total Price = Base Price + GST Amount

Example: Freelance service at ₹50,000 + 18% GST

Base Price = ₹50,000
GST Amount = ₹50,000 × 18% = ₹9,000
Total Invoice Amount = ₹50,000 + ₹9,000 = ₹59,000
CGST (9%) = ₹4,500 | SGST (9%) = ₹4,500 (for intra-state)

How to Remove GST from a Price (GST Inclusive Calculation)

Use this when you know the final price including GST and need to find the original base price and GST amount.

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

Example: Product priced at ₹1,180 inclusive of 18% GST

Total Price = ₹1,180
Base Price = ₹1,180 ÷ 1.18 = ₹1,000
GST Amount = ₹1,180 − ₹1,000 = ₹180

CGST, SGST and IGST — Which to Show on Invoice?

Transaction Type	Tax Components	Example
Intra-state (within same state)	CGST + SGST (equal split)	Karnataka seller + Karnataka buyer
Inter-state (different states)	IGST (full rate)	Karnataka seller + Maharashtra buyer
Export (outside India)	0% GST (zero-rated) or IGST with refund	Indian seller + foreign client

Intra-state Example — 18% GST split into CGST + SGST

Base Amount: ₹10,000
CGST @ 9%: ₹900
SGST @ 9%: ₹900
Total Invoice: ₹11,800

Inter-state Example — 18% GST as IGST

Base Amount: ₹10,000
IGST @ 18%: ₹1,800
Total Invoice: ₹11,800

GST Calculation Examples for Common Services

Service	Base Amount	GST Rate	GST Amount	Total
Website design	₹30,000	18%	₹5,400	₹35,400
CA consultation	₹5,000	18%	₹900	₹5,900
Restaurant bill (AC)	₹1,200	5%	₹60	₹1,260
Hotel room (above ₹7500)	₹8,000	18%	₹1,440	₹9,440
Mobile phone	₹20,000	12%	₹2,400	₹22,400

💡 Quick tip: Always double-check which GST rate applies to your specific goods or services. Rates can vary by HSN code (for goods) and SAC code (for services). When in doubt, consult the GST portal at gst.gov.in or a CA.

Frequently Asked Questions

Is there GST on freelance income?

Yes. Freelance and consulting services fall under 18% GST. If your annual service income exceeds ₹20 lakh (₹10 lakh in special category states), GST registration is mandatory and you must charge 18% GST on all invoices and file regular GST returns.

How do I calculate GST for a restaurant bill?

Restaurants without AC charge 5% GST (no input tax credit). Restaurants with AC charge 5% GST as well (changed from 18% in 2019). Branded restaurant chains may have different rates. Your restaurant bill should clearly show the base amount and GST amount separately.

Can I claim GST paid on my phone or laptop for my business?

Yes, if you are GST-registered, you can claim Input Tax Credit (ITC) on purchases made for your business — including laptops, phones, software subscriptions, and other business expenses. You cannot claim ITC on personal purchases. Maintain proper invoices with your GSTIN mentioned.

What is reverse charge mechanism in GST?

Under the Reverse Charge Mechanism (RCM), the recipient of goods or services pays the GST instead of the supplier. This applies in specific situations — for example, when a GST-registered business purchases from an unregistered vendor above a certain value. The registered business must pay GST directly to the government on such purchases.

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