GST Calculator

Free Online GST Calculator (India)

This GST calculator helps you quickly work out Goods and Services Tax on any transaction — whether you need to add GST on top of a base price for billing, or extract the GST component from a price that already includes tax. It also splits the tax into CGST and SGST for intrastate sales, or shows IGST for interstate sales, exactly as required on a GST-compliant invoice.

GST is one of the most common calculations for anyone running a business in India — shopkeepers, freelancers, restaurants, and e-commerce sellers all need to add or remove GST correctly on every invoice. This free calculator handles both directions of the calculation instantly, along with the correct tax-component split, so you always know exactly what to charge or what a price actually breaks down to.

What Is GST?

GST, or Goods and Services Tax, is an indirect tax charged on the supply of most goods and services in India. It replaced a range of older indirect taxes — like VAT, service tax, and excise duty — with a single, unified tax structure. GST is a destination-based tax, meaning it's collected at the point of consumption rather than the point of origin, and it's split between the central and state governments depending on whether a sale happens within a single state or across state lines.

GST Calculation Formula

GST calculation depends on whether your starting amount already includes tax or not:

• Adding GST (exclusive mode): GST Amount = Base Amount × (GST Rate ÷ 100), and Total Amount = Base Amount + GST Amount
• Removing GST (inclusive mode): Base Amount = Total Amount ÷ (1 + GST Rate ÷ 100), and GST Amount = Total Amount − Base Amount
• Intrastate sale: GST splits equally — CGST = GST Amount ÷ 2, and SGST = GST Amount ÷ 2
• Interstate sale: full GST is charged as IGST = GST Amount

How to Add GST to a Price — Step by Step

If your price doesn't yet include tax, here's how to add it:

• Step 1: Start with your base price (the amount before tax).
• Step 2: Multiply the base price by the GST rate, then divide by 100 to get the GST amount.
• Step 3: Add the GST amount to the base price to get the final, tax-inclusive total.
• Step 4: If it's an intrastate sale, split the GST amount equally into CGST and SGST for the invoice. If it's interstate, show the full amount as IGST.

How to Remove GST from a Price — Step by Step

If a price already includes tax and you need to find the original base amount:

• Step 1: Start with the GST-inclusive total.
• Step 2: Divide the total by (1 + GST Rate ÷ 100) to get the base amount.
• Step 3: Subtract the base amount from the total to get the GST amount that was included.

Worked Example — Adding GST

Add 18% GST to a base price of ₹10,000 for an intrastate sale.

• Step 1: GST Amount = ₹10,000 × 18 ÷ 100 = ₹1,800.
• Step 2: Total Amount = ₹10,000 + ₹1,800 = ₹11,800.
• Step 3: Since it's intrastate, CGST = ₹900 and SGST = ₹900 (₹1,800 split equally).

Worked Example — Removing GST

Find the base price from a GST-inclusive amount of ₹11,800 at 18% GST.

• Step 1: Base Amount = ₹11,800 ÷ 1.18 = ₹10,000.
• Step 2: GST Amount = ₹11,800 − ₹10,000 = ₹1,800.

How GST is Calculated

A quick summary of the four core rules this calculator applies:

• Adding GST: Total Amount = Base Amount + (Base Amount × GST Rate ÷ 100)
• Removing GST: Base Amount = Total Amount ÷ (1 + GST Rate ÷ 100)
• Intrastate sale: GST splits equally into CGST (Central GST) and SGST (State GST)
• Interstate sale: full GST is charged as IGST (Integrated GST)

Current GST Slabs in India

GST in India is charged under a few standard slabs depending on the goods or service category:

• 0% — essential items like fresh food, milk, books
• 5% — packaged food, footwear, transport services
• 12% — processed food, business-class travel, some electronics
• 18% — most goods and services, including IT, telecom, and financial services
• 28% — luxury and sin goods like cars, tobacco, aerated drinks

CGST, SGST, and IGST Explained

When a sale happens within the same state (intrastate), GST is split equally between the central government and the state government — collected as CGST (Central GST) and SGST (State GST). For example, an 18% GST rate becomes 9% CGST plus 9% SGST. When a sale happens between two different states (interstate), the full GST amount is collected as a single tax called IGST (Integrated GST), which is later apportioned between the central government and the destination state. Every GST invoice must correctly show this breakup, which is exactly what the chart on this calculator visualizes.

Why This Matters for Your Business

For shopkeepers, restaurants, freelancers, and small businesses, showing the correct CGST/SGST or IGST breakup isn't optional — it's required on every GST invoice, and errors can cause mismatches during GST return filing. Use this calculator to quickly cross-check your billing software, quote GST-inclusive prices to customers, or reverse-calculate the base price when a customer gives you a final, tax-included amount. It's also useful for shoppers who want to check whether a listed price already includes GST, or work out exactly how much tax they're paying on a purchase.

GST for E-commerce and Online Sellers

Online sellers often need to calculate GST separately for every order, since customers can be located in the same state or in different states, changing whether CGST+SGST or IGST applies to that specific sale. Marketplaces and invoicing tools generally handle this automatically, but understanding the underlying math helps when reconciling accounts, checking a marketplace's tax deduction, or setting prices that already build in the correct GST-inclusive amount for customers.

Common Mistakes When Calculating GST

A common mistake is applying the GST rate to a tax-inclusive amount using the exclusive formula (multiplying instead of dividing), which overstates the GST amount and the base price. Another frequent error is splitting GST into CGST and SGST for an interstate sale, or charging IGST for an intrastate sale — the split depends entirely on whether the buyer and seller are in the same state or different states, not on the type of goods being sold. It's also easy to apply the wrong slab rate, since GST rates vary significantly by product or service category, so always confirm the correct rate for your specific item before billing.

Why Use This GST Calculator?

This tool handles both adding and removing GST instantly, along with the correct CGST/SGST or IGST split, visualized in a clear price breakdown and tax-component chart. Whether you're billing a customer, checking an invoice, filing a GST return, or just want to know how much tax is included in a price, this calculator gives you an accurate, compliant answer in seconds.