GST Calculator

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What This Tool Does

This calculator works out the Goods and Services Tax on any product or service in seconds. Enter the base amount and the applicable GST rate, then choose whether your price already includes GST or not. The tool returns the GST amount, the pre-tax price, and the final payable amount — no manual formula needed.

How It's Calculated

GST is applied as a percentage of the transaction value. The formula works in two directions depending on whether your price is GST-exclusive or GST-inclusive.

When the price excludes GST (adding GST on top):

GST Amount = Original Price × (GST Rate ÷ 100)

Total Price = Original Price + GST Amount

When the price includes GST (removing GST from the total):

Original Price = Total Price ÷ (1 + GST Rate ÷ 100)

GST Amount = Total Price − Original Price

Worked Example

You buy a service worth ₹10,000 at 18% GST:

• GST exclusive: ₹10,000 × 18% = ₹1,800 GST → Total = ₹11,800
• GST inclusive: ₹11,800 ÷ 1.18 = ₹10,000 original → GST = ₹1,800

Both routes give the same GST amount — the starting point is what differs.

CGST, SGST, and IGST Breakdown

When GST applies to a transaction, it is split depending on whether the sale is within a state or across state lines.

Intra-state transactions (within the same state):
The GST is split equally between CGST (Central GST) and SGST (State GST). On an 18% GST transaction, 9% goes to the central government as CGST and 9% to the state government as SGST.

Inter-state transactions (across states or imports):
A single IGST (Integrated GST) applies at the full rate. The central government collects it and distributes the state's share to the destination state.

Union Territory transactions:
UTGST replaces SGST for supplies made in any of the seven union territories, and is collected alongside CGST.

GST Slabs in India

GST in India currently applies across four main rate slabs:

• 0% — Essential items such as fresh produce, milk, and certain food grains
• 5% — Basic necessities including packaged food, transport services, and some medicines
• 12% / 18% — Most goods and services including electronics, restaurants, financial services, and construction
• 28% — Luxury and demerit goods such as automobiles, tobacco, and aerated drinks

Some goods are exempt from GST entirely. When in doubt about which slab applies to a specific product or service, check the official GST rate schedule or consult a tax professional.

Edge Cases and Special Rules

Composition scheme: Small businesses below a certain annual turnover threshold can opt for the GST composition scheme, which applies a flat lower rate. Standard GST calculations do not apply to these businesses.

Input Tax Credit (ITC): Registered businesses can claim credit for GST paid on purchases against their GST liability on sales. The net GST payable may therefore differ from what this calculator shows, which reflects gross GST on a single transaction.

Reverse charge mechanism: In certain categories, the buyer — not the seller — is liable to pay GST directly to the government. The calculator does not account for this scenario.

GST on exports: Exports are generally zero-rated under GST, meaning no GST is charged on the transaction.

Who Uses This

• Small business owners calculating GST to add to invoices before billing clients
• Freelancers and consultants working out tax on service fees
• Shoppers and buyers checking whether a quoted price is inclusive or exclusive of tax
• Accountants and bookkeepers doing quick transaction-level checks
• Students and exam aspirants practising GST formula problems

GST vs. the Old Tax Regime

Before GST came into effect in July 2017, India had multiple overlapping indirect taxes — VAT, service tax, excise duty, and others — each with different rates and filing requirements. GST replaced all of these with a single unified tax across the country. The key practical difference: under the old system, tax was collected at multiple points in the supply chain; under GST, it is collected at the final stage with credits passed along at each step.

FAQ

What is the GST rate on services?

Most services fall under the 18% slab, though some — such as basic healthcare and education — are exempt, and others like restaurant services are taxed at 5%. Always verify the applicable rate for your specific service category.

How do I calculate 18% GST on a price?

Multiply the base price by 0.18 to get the GST amount, then add it to the base price for the total. Example: ₹5,000 × 0.18 = ₹900 GST → Total = ₹5,900.

What is the difference between CGST and SGST?

Both apply to sales within the same state at equal rates — each takes half the total GST rate. CGST goes to the central government, SGST to the state government.

Can I use this calculator for both goods and services?

Yes. The formula is the same regardless of whether the transaction involves goods or services. The only variable is the applicable GST rate, which differs by category.

Is GST applicable on all products in India?

No. Certain essential items — fresh vegetables, milk, eggs, and some grains — are exempt from GST. Petroleum products, alcohol for human consumption, and electricity are also outside the GST framework and taxed separately by state governments.

A Note on Results

This calculator is for quick reference and general planning only. Tax liability in practice depends on your GST registration status, applicable exemptions, input tax credits, and the specific nature of the transaction. For filing, compliance, or business-level tax advice, consult a chartered accountant or registered GST practitioner.