GST Calculator

What is GST?

GST (Goods and Services Tax) is a single, comprehensive indirect tax levied on the supply of goods and services. Introduced in India on 1 July 2017, it replaced a tangle of earlier indirect taxes — VAT, service tax, excise duty and many others — with one unified system applied across the country. GST is a destination-based tax, meaning it is collected by the state where the goods or services are ultimately consumed rather than where they are produced.

For businesses and consumers alike, the practical question is usually simple: how much GST applies to a given amount, and what is the final price? This GST Calculator answers that instantly. Enter an amount, choose whether you want to add GST to a base price or remove GST from a price that already includes it, pick the applicable rate, and you immediately see the original amount, the GST amount (split into CGST and SGST), and the final amount. Everything is calculated in your browser, so your figures stay completely private.

How GST works

GST is a value-added tax, which means it is charged at every stage of the supply chain but only on the value added at that stage. A manufacturer pays GST on raw materials and charges GST on the finished goods; a wholesaler and retailer do the same. Crucially, each business can claim credit for the GST it has already paid on its purchases — this is called Input Tax Credit — so tax is not charged on tax. The end consumer ultimately bears the GST, because they are the last link in the chain and cannot claim a credit. This design eliminates the "cascading" effect of the old system, where taxes were levied on top of other taxes, and it is one of the main reasons GST was introduced.

GST rate slabs in India

GST in India is organised into several rate slabs, so that essentials are taxed lightly (or not at all) while luxury and "sin" goods are taxed heavily. The four main rates this calculator supports are:

• 5% — applied to many essential and mass-consumption items, such as packaged food staples, economy footwear, life-saving drugs and economy transport.
• 12% — a middle band covering items like processed foods, business-class air travel, certain apparel and mobile phones.
• 18% — the most common slab, applied to the majority of goods and services, including most electronics, restaurants, financial services, soaps and industrial intermediates.
• 28% — the highest slab, reserved for luxury and non-essential goods such as cars, air conditioners, premium products and tobacco (often with an additional cess on top).

In addition, a 0% (nil) rate applies to many unbranded basics such as fresh fruit and vegetables, milk and unbranded grains, and a special 3% rate applies to gold. Because the slab depends on the specific product or service, always confirm the correct rate for your item before relying on a figure. This calculator lets you select any of the four main slabs with a single tap, or enter a custom rate if you need one.

GST-exclusive vs GST-inclusive amounts

One of the most common sources of confusion is whether a price already includes GST. There are two scenarios, and this calculator handles both:

GST-exclusive (adding GST). The amount you have is the base price before tax, and you want to add GST to find the final price. This is the situation when you are quoting or invoicing: you know your net price and need to add tax on top.

GST-inclusive (removing GST). The amount you have is the final price that already includes GST, and you want to work backwards to find the base price and how much of the total was tax. This is the situation when you have a receipt or an all-inclusive price and need to know the tax component — for accounting, for claiming input credit, or simply to understand what you paid.

Choosing the wrong mode is a frequent mistake that leads to incorrect figures, so the calculator makes the choice explicit with a clear toggle. Switching between the two modes recalculates everything instantly.

How to calculate GST

The formulas are straightforward once you know which direction you are working in.

To add GST to a base amount:

GST amount = Base amount × (GST rate ÷ 100)
Final price = Base amount + GST amount

For example, on a base amount of 1,000 at 18% GST, the GST amount is 1,000 × 0.18 = 180, and the final price is 1,180. The 180 of GST is split equally into 90 CGST and 90 SGST for an intra-state sale.

To remove GST from an inclusive amount:

Base amount = Inclusive amount × 100 ÷ (100 + GST rate)
GST amount = Inclusive amount − Base amount

For example, if a price of 1,180 already includes 18% GST, the base amount is 1,180 × 100 ÷ 118 = 1,000, so the GST component is 180. Notice that you cannot simply take 18% of the inclusive price — that would give the wrong answer. Extracting GST requires dividing by (100 + rate), which is exactly what this calculator does for you.

Reverse GST calculation explained

Removing GST from an inclusive price — sometimes called reverse GST or back-calculation — trips up many people, so it is worth dwelling on. The instinct is to multiply the total by the rate, but because the total already contains the tax, that overstates the GST. The correct approach is to recognise that the inclusive price represents 100% of the base plus the rate; at 18%, the total is 118% of the base. Dividing the total by 1.18 recovers the base, and the remainder is the tax. The same logic applies to every slab: divide by 1.05 for 5%, 1.12 for 12%, and 1.28 for 28%. This calculator performs the division precisely, so you always get the accurate tax component from any inclusive amount.

CGST, SGST, IGST and UTGST

India's GST is actually collected in components, depending on whether a sale is within a state or between states. For a transaction within the same state (intra-state), the total GST is split equally into CGST (Central GST), which goes to the central government, and SGST (State GST), which goes to the state government. So 18% GST on an intra-state sale is really 9% CGST plus 9% SGST. This calculator shows that split automatically, which is exactly how it appears on a compliant tax invoice.

For a transaction between two different states (inter-state), a single IGST (Integrated GST) is charged instead, at the full rate, and is later apportioned between the centre and the destination state. In Union Territories without a legislature, UTGST takes the place of SGST. The total tax you pay is the same in every case — the components simply route the revenue to the right governments. For a quick price calculation you only need the total rate; the CGST/SGST breakdown shown here is for intra-state invoicing.

Input Tax Credit

A defining feature of GST is Input Tax Credit (ITC). A registered business can deduct the GST it has paid on its business purchases (inputs) from the GST it collects on its sales (outputs), and pay only the difference to the government. This ensures tax is levied only on the value each business adds, and it is why GST avoids the cascading taxes of the old regime. Although this calculator focuses on computing GST on a single amount, understanding ITC explains why businesses care so much about correctly separating the tax component from a price — that separated GST is precisely what can be claimed as credit.

Who needs to register for GST?

In India, GST registration is generally mandatory once a business's aggregate annual turnover exceeds a threshold — commonly ₹40 lakh for goods and ₹20 lakh for services, with lower limits in some special-category states. Registration is also required for inter-state suppliers, e-commerce operators and certain other categories regardless of turnover. Registered businesses must charge GST, issue GST-compliant invoices that show the CGST/SGST or IGST split, file periodic returns, and remit the net tax after claiming input credit. Even if you are not registered, knowing how GST is calculated helps you understand the prices you pay and check that invoices are correct.

GST-inclusive vs exclusive pricing for businesses

How you display prices has real consequences, and the right choice depends on who you sell to. Businesses selling to other businesses (B2B) usually quote GST-exclusive prices, because their customers can claim the GST back as input tax credit and care about the net figure. Businesses selling to consumers (B2C) typically advertise GST-inclusive prices, because the customer pays the all-in amount and expects the shelf price to be the final price. Getting this wrong causes disputes and accounting errors: quote an exclusive price as if it were inclusive and you absorb the tax yourself; do the reverse and you overcharge the customer. This calculator lets you switch instantly between the two views, so you can confirm both the net price and the final price before you publish a quote, print a price list, or raise an invoice.

Common GST calculation mistakes

A handful of mistakes account for most GST errors. The most common, by far, is treating an inclusive price as exclusive — taking a simple percentage of a price that already contains the tax, which overstates the GST. As shown above, you must divide an inclusive amount by (100 + rate), not multiply it by the rate. Another frequent error is using the wrong slab: rates differ by product, and applying 18% to an item taxed at 12% (or vice versa) produces an invoice that will not reconcile. A third is rounding too early; rounding the base and the tax independently before adding them can leave the totals a rupee out, so it is best to round only the final figures. Finally, businesses sometimes forget the CGST/SGST split on intra-state invoices, or mistakenly apply CGST and SGST to an inter-state sale that should carry IGST. This calculator helps you avoid all of these by computing the base, the tax, the CGST/SGST split and the final amount together, from a single, explicit choice of direction and rate.

GST and VAT around the world

While this calculator is built around India's GST slabs, the underlying value-added-tax concept is used in more than 160 countries, usually under the name GST or VAT. Australia, for example, applies a flat 10% GST; New Zealand uses 15%; Singapore's GST has risen in steps to 9%; Canada combines a federal GST with provincial taxes; and the United Kingdom and the European Union levy VAT at standard rates around 20%, with reduced rates for essentials. The arithmetic is identical everywhere — add the rate to a net price, or divide an inclusive price by (100 + rate) to extract the tax — so you can use this tool for any single-rate VAT or GST simply by entering the relevant rate in the custom field. Only the rate and the local rules about which goods fall into which band change from country to country.

The GST composition scheme

India offers a simplified composition scheme for small businesses below a turnover threshold, under which they pay GST at a low flat rate on turnover (for example 1% for traders or 5% for restaurants) instead of the standard slab, and file simpler returns. The catch is that composition dealers cannot charge GST separately on their invoices or claim input tax credit — they absorb the tax themselves. If you operate under the composition scheme you generally will not be itemising CGST and SGST to customers, but you may still use a calculator like this one to work out your flat-rate liability on a given turnover by entering your composition rate as a custom rate.

Benefits of using a GST calculator

Calculating GST by hand is error-prone, especially when extracting tax from inclusive prices or splitting it into CGST and SGST. A dedicated calculator removes that risk and saves time: it gives instant, accurate figures, shows the full breakdown a compliant invoice needs, and lets you compare scenarios — different rates, inclusive versus exclusive — in seconds. Because this tool runs entirely in your browser, it also keeps your financial figures completely private, with nothing uploaded or stored. For business owners, accountants, freelancers and shoppers alike, it turns a fiddly calculation into a one-step answer.

Using this GST calculator

To use the calculator, enter your amount, choose whether to add or remove GST, and select the applicable rate of 5%, 12%, 18% or 28% (or type a custom rate). The original amount, GST amount with its CGST and SGST split, and the final amount update instantly as you type — there is no button to press and nothing is sent to a server. Whether you are a business owner preparing an invoice, an accountant reconciling a receipt, or a shopper checking how much tax is in a price, this tool gives you fast, accurate GST figures while keeping your numbers private. Bookmark it for the next time you need to add or extract GST in seconds.