GST Calculator — Calculate GST, CGST, SGST & IGST Online | AliGreat.com

Free GST Calculator for India — add or extract GST at 0%, 5%, 12%, 18% or 28%, with automatic CGST/SGST or IGST split for any invoice.

Whether you’re a freelancer raising an invoice, a small business owner pricing a product, or simply trying to verify a bill, GST calculations trip up more people than they should — mainly because “adding 18% GST” and “extracting 18% GST from an inclusive price” are two genuinely different calculations that are easy to confuse. The GST Calculator on AliGreat.com handles both directions correctly, along with the CGST/SGST versus IGST split that depends on where the supply is happening.

What does the GST Calculator do?

Enter an amount, select the applicable GST rate (0%, 5%, 12%, 18%, or 28%), specify whether your entered amount is GST-exclusive (and GST needs to be added) or GST-inclusive (and GST needs to be extracted from within it), and select whether the supply is intra-state (attracting CGST + SGST) or inter-state (attracting IGST). The calculator instantly shows the taxable value, GST amount, the CGST/SGST or IGST split, and the final invoice total.

The formula behind it

Two distinct formulas apply, depending on whether your amount is exclusive or inclusive of GST:

Exclusive (adding GST to a base price): GST = Amount × Rate, and Total = Amount + GST

Inclusive (extracting GST from a price that already includes it): GST = Amount × Rate / (100 + Rate), and Base Value = Amount − GST

The critical mistake many people make is applying the exclusive formula (a straightforward percentage multiplication) to an inclusive amount — this always overstates the actual GST component, since it fails to account for the fact that the rate needs to be applied to the base value, not to the already-tax-inclusive total.

A worked example — exclusive calculation

Suppose you’re quoting a service at ₹10,000, exclusive of GST, at the standard 18% rate, for an intra-state supply.

GST = 10,000 × 18% = ₹1,800 Total invoice = 10,000 + 1,800 = ₹11,800

Since this is an intra-state supply, the ₹1,800 GST splits equally: CGST = ₹900, SGST = ₹900.

A worked example — inclusive calculation

Now suppose a retail product is priced at ₹11,800, already inclusive of 18% GST, and you need to know the actual taxable value and GST component within that price.

GST = 11,800 × 18 / (100 + 18) = 11,800 × 18/118 = ₹1,800 Taxable value = 11,800 − 1,800 = ₹10,000

Notice this produces exactly the same GST amount as the exclusive example above, since both examples describe the same underlying transaction viewed from two different starting points — but if you’d mistakenly applied the simple exclusive formula (₹11,800 × 18% = ₹2,124) to this inclusive price instead, you’d have overstated the GST component by ₹324 and understated the true taxable value accordingly. This exact confusion is one of the most common GST calculation errors, and it’s precisely what this calculator’s exclusive/inclusive toggle is built to prevent.

CGST, SGST, and IGST — understanding the split

India’s GST is a destination-based tax, meaning it’s ultimately collected by the state where goods or services are actually consumed, not where they’re supplied from. For an intra-state supply (buyer and seller in the same state), the GST amount is split equally between CGST (Central GST, going to the central government) and SGST (State GST, going to the state government) — each getting exactly half of the total GST amount. For an inter-state supply (buyer and seller in different states), the entire GST amount is instead levied as a single IGST (Integrated GST), collected by the central government and subsequently apportioned to the destination state through a settlement mechanism between the centre and states.

This distinction matters practically for invoicing and GST return filing — an intra-state invoice must show CGST and SGST as separate line items, while an inter-state invoice shows a single IGST line item. Getting this split wrong on an invoice (showing CGST/SGST for what’s actually an inter-state supply, or vice versa) is a common compliance error that this calculator’s place-of-supply toggle helps you avoid.

India’s GST rate slabs, and what typically falls into each

• 0% (Nil-rated/exempt): essential items like fresh fruits and vegetables, unbranded food grains, and certain essential services
• 5%: items considered necessities but not entirely exempt, such as packaged food items, footwear below a certain price point, and some transport services
• 12%: a middle slab covering items like certain processed foods, business-class air travel, and some construction materials
• 18%: the most common slab, covering the majority of services (including most professional and consulting services), electronics, and many manufactured goods
• 28%: the highest standard slab, covering luxury and “sin” goods like automobiles, tobacco products, and aerated beverages, often with an additional compensation cess layered on top for specific items in this category

Because slab classification depends on the specific HSN (Harmonized System of Nomenclature) code for goods, or SAC (Services Accounting Code) for services, always confirm the exact applicable rate for your specific product or service from official GST rate notifications or a tax professional — this calculator computes the tax correctly once you know the rate, but doesn’t determine which rate applies to a specific item.

GST compensation cess — an important addition for specific goods

Certain luxury and sin goods within the 28% slab — such as automobiles, tobacco products, and aerated drinks — attract an additional GST compensation cess on top of the standard 28% GST rate, sometimes substantially increasing the total tax burden on these specific items. This calculator computes standard GST at your selected rate but does not separately add compensation cess — if you’re calculating GST for an item known to attract cess, you’ll need to add that component separately based on the specific cess rate applicable to that item category.

Reverse charge mechanism — a different GST scenario entirely

For certain specified categories of supply, GST liability shifts from the supplier to the recipient under what’s called the reverse charge mechanism (RCM) — common examples include certain services received from unregistered suppliers, or specific categories like goods transport agency services. This calculator computes standard forward-charge GST (where the supplier collects and remits GST) and doesn’t specifically model reverse charge scenarios, which involve a different compliance and payment flow even though the underlying rate calculation itself uses the same basic percentage mathematics.

Input Tax Credit — why GST paid isn’t always a final cost

For GST-registered businesses, GST paid on business purchases (input GST) can generally be claimed as a credit against GST collected on sales (output GST), meaning the GST calculated by this tool often isn’t a final, absorbed cost for a registered business the way it would be for an end consumer — it’s a pass-through amount that nets out against input credits when filing periodic GST returns. This calculator is useful for computing the correct GST amount to charge on an invoice or to identify within a price, but doesn’t model the separate input tax credit reconciliation process businesses undertake during return filing.

Who should use this calculator

Freelancers and small business owners raising invoices who need to correctly add GST to a quoted price, retailers or consumers trying to work out the actual taxable value and tax component within an already GST-inclusive price, and anyone needing to determine the correct CGST/SGST versus IGST split for a specific transaction based on the buyer and seller’s location will find this calculator directly useful for quick, accurate calculations.

Frequently asked questions

What’s the difference between GST-inclusive and GST-exclusive pricing? Exclusive pricing means GST needs to be added on top of the quoted amount; inclusive pricing means the quoted amount already contains GST within it, and the tax component needs to be extracted rather than added — using the wrong formula for either scenario produces an incorrect result.

How do I know if a transaction is intra-state or inter-state? This is determined by the location of the supplier and the place of supply (generally the buyer’s location) as defined under GST law — if both fall within the same state, it’s intra-state (CGST+SGST); if they fall in different states, it’s inter-state (IGST).

Does this calculator tell me which GST rate applies to my product or service? No — you need to determine the correct HSN or SAC code and its associated rate separately, from official GST rate schedules or a tax professional; this calculator computes the tax correctly once you’ve identified the applicable rate.

Is GST compensation cess included in this calculator’s output? No — compensation cess, which applies to specific luxury and sin goods within the 28% slab, needs to be calculated and added separately, as it varies by specific item category.

Try it now

Open the GST Calculator on AliGreat.com, enter your amount and select your rate, mode, and supply type, and get the correct GST breakdown instantly — free and fully transparent about the calculation used.