GST Calculator (India)

What is GST?

The Goods and Services Tax (GST) is India's unified indirect tax introduced on 1 July 2017, replacing a maze of central and state taxes (VAT, service tax, excise duty, octroi). It applies to almost every sale of goods and services in India, with five standard rate slabs: 0%, 5%, 12%, 18%, and 28%. A few items like petroleum, alcohol for human consumption, and electricity are still outside GST.

How GST is split

When the buyer and seller are in the same state, the total GST is split equally between the central government (CGST) and the state government (SGST). For an 18% rate, that's 9% CGST + 9% SGST. When they are in different states, the entire tax is collected as IGST (Integrated GST) by the centre, which then shares it with the destination state. This calculator handles both cases — pick the transaction type from the dropdown.

Real example

A small business in Chennai sells a laptop worth ₹50,000 (base price). At the standard 18% GST rate, here's how the calculation works:

• Base price: ₹50,000
• Total GST (18%): ₹9,000
• Final invoice value: ₹59,000

If the buyer is also in Tamil Nadu (intra-state sale), the ₹9,000 splits as ₹4,500 CGST plus ₹4,500 SGST. If the buyer is in Karnataka (inter-state sale), the full ₹9,000 is charged as IGST. To work backwards from a tax-inclusive price, switch to Remove GST mode: a restaurant bill of ₹2,360 (with 18% GST) breaks down to ₹2,000 base price plus ₹360 GST.

How to use the calculator

1. Choose Add GST if you have a base price and need to know the final price including GST. Choose Remove GST if you have a tax-inclusive price (e.g., a restaurant bill) and want to find the base value.
2. Enter the amount and pick the GST rate.
3. Pick intra-state or inter-state to see the right tax split.
4. Click Calculate GST.

GST formulas

Adding GST: GST amount = (Base price × Rate) ÷ 100; Final price = Base price + GST.
Removing GST: Base price = Final price ÷ (1 + Rate/100); GST amount = Final price − Base price.

Worked example: invoice in Chennai

A small business in Chennai sells a laptop worth ₹50,000 (base price). At the standard 18% GST rate, here's how the calculation works:

• Base price: ₹50,000
• Total GST (18%): ₹9,000
• Final invoice value: ₹59,000

If the buyer is also in Tamil Nadu (intra-state sale), the ₹9,000 splits as ₹4,500 CGST + ₹4,500 SGST. If the buyer is in Karnataka (inter-state sale), the full ₹9,000 is charged as IGST. To work backwards from a tax-inclusive price, switch to Remove GST mode: a restaurant bill of ₹2,360 (with 18% GST) breaks down to ₹2,000 base price plus ₹360 GST.

India's GST rate slabs

The Goods and Services Tax replaced a maze of central and state taxes in July 2017. It applies to almost every sale of goods and services in India, organised into five main slabs:

• 0% — fresh fruits and vegetables, milk, fresh fish, fresh meat, eggs, bread, salt, books, newspapers, education, healthcare
• 5% — packaged food, branded paneer, edible oils, life-saving drugs, footwear under ₹1,000, economy-class air tickets
• 12% — processed food, butter, ghee, ayurvedic medicines, business-class flights, tickets for circus and theatre
• 18% — most goods and services, restaurant bills, telecom, software, salon and spa services, IT services, branded apparel above ₹1,000
• 28% — luxury and "sin" items: cars, motorcycles above 350cc, tobacco products, aerated drinks, premium hotels above ₹7,500/night

Rates do change. The official source is the GST Council's notifications on cbic.gov.in. For specific products, look up your HSN code.

CGST + SGST versus IGST

India runs a dual GST system. The total rate is the same, but who collects it depends on whether the buyer and seller are in the same state. Intra-state sale (same state): the rate splits 50/50 between CGST (Centre) and SGST (State). Inter-state sale (different states): the entire rate is charged as IGST, collected by the Centre and later shared with the destination state. Same total tax, different revenue split.

Common GST mistakes

The biggest mistakes Indian small businesses make: charging GST without registering (illegal — but the collected amount must still be deposited with the government), wrong place-of-supply for services (place-of-supply rules can override the buyer's address), and forgetting reverse charge mechanism for legal fees and goods transport agency services.

Disclaimer

This calculator produces estimates based on standard GST rates as of May 2026. Rates change with each GST Council meeting; always cross-check the latest notifications at cbic.gov.in before issuing invoices. Some categories (real estate, restaurants, hotels) have special composition rates. For business GST advice, consult a GST-registered Chartered Accountant.

Frequently asked questions