GST Calculator India — Calculate GST Online for All Tax Slabs

Goods and Services Tax (GST) replaced a complex web of central and state taxes in India when it was introduced on July 1, 2017. Today, GST is applied to the supply of nearly every good and service in India, and understanding how to calculate it accurately is essential for business owners, freelancers, accountants, and consumers alike.

Whether you need to add GST to an invoice price or extract the base price from a GST-inclusive amount, our free GST calculator handles both operations instantly for all Indian tax slabs. This guide explains the complete GST framework — slabs, formulas, CGST/SGST/IGST breakdown, and registration requirements.

What Is GST?

Goods and Services Tax (GST) is a comprehensive, multi-stage, destination-based indirect tax levied on every value addition in the supply chain. It replaced multiple central taxes (Excise Duty, Service Tax, CST, etc.) and state taxes (VAT, Entertainment Tax, Luxury Tax, etc.) with a single unified tax system.

GST is described as "one nation, one tax, one market." It is a destination-based tax — collected at the point of consumption rather than production. If a product is manufactured in Maharashtra but sold to a consumer in Karnataka, the tax revenue goes to Karnataka.

GST operates on the principle of input tax credit (ITC): at each stage of the supply chain, businesses can claim credit for the GST they paid on their purchases (inputs), and pay GST only on the value they add. This prevents the cascading ("tax on tax") effect that was a major flaw in the old indirect tax system.

GST Slabs — 0%, 5%, 12%, 18%, 28%

The GST Council has placed goods and services into five tax slabs:

GST Rate	Category Examples
0% (Nil)	Fresh fruits, vegetables, milk, eggs, bread, salt, cereals (unpacked), educational services, healthcare
5%	Packaged food items, tea, coffee, edible oils, fertilisers, transport services, economy class air travel, textile (job work)
12%	Computers, processed food, butter, ghee, mobile phones, umbrellas, business class air travel
18%	Most services (IT, consultancy, banking fees), air conditioners, refrigerators, washing machines, biscuits, restaurant services (AC), hotel rooms (₹7,501–₹12,499/night)
28%	Luxury goods (cars, motorcycles, tobacco products, aerated drinks, casinos, pan masala), 5-star hotels

In addition to these five standard slabs, a compensation cess is levied over and above 28% on some luxury and demerit goods (e.g., luxury cars attract 28% + 15–22% cess). The specific GST rate for any item is determined by its HSN (Harmonised System of Nomenclature) code for goods and SAC (Service Accounting Code) for services.

GST Calculation Formulas

There are two scenarios: adding GST to a base price (exclusive), and extracting GST from a price that already includes it (inclusive).

Adding GST to a Base Price (Exclusive)

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

Example: Base price ₹10,000, GST rate 18%
GST = 10,000 × 0.18 = ₹1,800
Total = 10,000 + 1,800 = ₹11,800

Extracting GST from an Inclusive Price

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

Example: Inclusive price ₹11,800, GST rate 18%
Base = 11,800 × 100 / 118 = 11,800 × 0.8475 = ₹10,000
GST = 11,800 − 10,000 = ₹1,800

Our GST calculator handles both operations with a simple toggle and automatically splits the result into CGST and SGST (for intra-state) or IGST (for inter-state).

GST Inclusive vs Exclusive

Understanding whether a quoted price includes GST or excludes it is critical — and surprisingly often a source of confusion and disputes.

GST Exclusive (ex-GST): The stated price does not include GST. You add GST on top. B2B transactions and quoted wholesale prices are often exclusive of GST. The invoice shows: Base Price + GST = Total.

GST Inclusive (inc-GST): The stated price already includes GST. This is common in retail consumer pricing and restaurant bills. To find the base price and GST component, you need the reverse formula above.

Consumer protection rules in India require that any price displayed to consumers include all applicable taxes — so a restaurant menu showing ₹350 for a dish should mean ₹350 is the total price you pay, with GST already included (or clearly stated as additional). Confusion arises most often with online platforms, where some display prices exclusive of GST with charges added at checkout.

CGST, SGST & IGST Explained

GST in India is a dual structure — both the Central Government and State Governments levy tax simultaneously on every transaction. The split depends on whether the transaction is intra-state (within one state) or inter-state (between different states).

Tax Type	Full Form	When Applied	Revenue Goes To
CGST	Central GST	Intra-state supply	Central Government
SGST	State GST	Intra-state supply	State Government
IGST	Integrated GST	Inter-state supply & imports	Central (later transferred to consuming state)
UTGST	Union Territory GST	Intra-UT supply	Union Territory

For intra-state transactions, the GST rate is split equally: a 18% GST splits into 9% CGST + 9% SGST. For inter-state transactions, the full 18% is charged as IGST. The supplier charges and collects IGST, and the central government distributes the state's share to the destination state government.

Example: A Delhi-based manufacturer sells goods to a Mumbai buyer at ₹50,000 attracting 12% GST.
This is an inter-state sale → IGST = 12% of ₹50,000 = ₹6,000 (IGST only, no CGST/SGST split)

Example: A Pune-based manufacturer sells to a Mumbai buyer at ₹50,000 attracting 12% GST.
This is an intra-state (Maharashtra to Maharashtra) sale → CGST = 6% = ₹3,000 + SGST = 6% = ₹3,000 (Total GST = ₹6,000)

GST Invoice Requirements

A GST-compliant tax invoice is the foundational document for claiming Input Tax Credit. A missing or non-compliant invoice means the buyer cannot claim ITC on that purchase. Mandatory components of a GST invoice include:

• Supplier's name, address, and GSTIN
• Invoice number (unique, sequential) and date
• Recipient's name, address, and GSTIN (for B2B transactions)
• HSN code (for goods) or SAC code (for services)
• Description, quantity, and unit of goods/services
• Taxable value and applicable discounts
• Rate and amount of CGST + SGST or IGST separately
• Total invoice value in words and figures
• Signature of authorised signatory

E-invoicing (electronic invoice) is mandatory for businesses with annual turnover above ₹5 crore (as of 2023 rules). The invoice is generated on the GST portal and receives a unique Invoice Reference Number (IRN) and QR code.

Who Must Register for GST?

GST registration is mandatory for certain businesses regardless of turnover, and for others once they cross a threshold:

Business Type	Mandatory Registration Threshold
Goods supplier (regular states)	Annual turnover > ₹40 lakh
Service provider (regular states)	Annual turnover > ₹20 lakh
Goods supplier (special category states)	Annual turnover > ₹20 lakh
Service provider (special category states)	Annual turnover > ₹10 lakh
E-commerce sellers (as aggregators)	Mandatory regardless of turnover
Inter-state supply of goods	Mandatory regardless of turnover
Casual taxable persons	Mandatory regardless of turnover

Voluntary registration is allowed even below these thresholds, which may be advantageous for businesses that want to claim ITC on their purchases or enhance credibility with B2B customers.

GST Returns Filing

Registered GST taxpayers must file periodic returns. The main return types are:

• GSTR-1: Outward supplies — monthly (if turnover > ₹5 crore) or quarterly. Details of sales invoices.
• GSTR-3B: Monthly summary return with net tax payable. Due by 20th of the following month.
• GSTR-9: Annual return summarising all transactions for the year. Due by December 31 of the following year.
• GSTR-2A/2B: Auto-populated from suppliers' GSTR-1, showing inward supplies for ITC matching.

Late filing attracts a penalty of ₹50 per day (₹20 for nil returns) plus applicable interest on unpaid tax. GST returns can be filed online via the GST portal (gst.gov.in) or through GST-compliant accounting software.

Input Tax Credit (ITC)

Input Tax Credit is the mechanism that eliminates cascading taxes in the GST system. It allows a registered taxpayer to deduct the tax paid on purchases (inputs) from the tax liability on sales (output). Only the net tax — the difference between output tax and input tax — is actually paid to the government.

Example: A manufacturer buys raw materials for ₹1,00,000 + 18% GST = ₹18,000 paid as input tax. Manufactures goods and sells for ₹1,50,000 + 18% GST = ₹27,000 output tax.
Net GST payable = ₹27,000 − ₹18,000 = ₹9,000 (ITC of ₹18,000 is claimed)

ITC can only be claimed on valid GST invoices, for business purposes, and against suppliers who have filed their returns. ITC is not available on personal expenses, exempted supplies, or certain blocked credits (motor vehicles for personal use, food and beverages, club memberships, etc.).

Frequently Asked Questions