GST Calculator

Exclusive vs Inclusive GST, and CGST/SGST vs IGST

Exclusive means the amount you enter is the base price, and GST is added on top — this is how most B2B invoices are quoted. Inclusive means GST is already baked into the amount you enter (common for MRP-labeled retail goods), and the calculator works backward to extract the base price and the tax component.

Whether GST is split as CGST+SGST or charged as IGST depends on whether the supplier and the place of supply are in the same state or different states — intra-state supplies split the rate equally between CGST and SGST (both going to different governments), while inter-state supplies charge the full rate as a single IGST. The total tax rate is the same either way; only how it's labeled and divided changes.

Worked Examples

A ₹1,00,000 base amount at 18% GST:

A ₹1,18,000 GST-inclusive amount at 18% works backward to the same figures:

Common GST Rate Slabs

Rate slabs and item classifications are revised periodically by the GST Council — confirm the current rate for your specific HSN/SAC code rather than assuming it hasn't changed, especially for goods near a slab boundary.

Claiming Input Tax Credit

A registered business that pays GST on its purchases (inputs) can generally set that off against the GST it collects on its own sales (output), paying only the net difference to the government. This isn't automatic on every purchase, though — ITC is available only for purchases used in the course of business, requires the supplier to have actually filed and paid the tax on their end, and specific categories of expenses are blocked from ITC regardless (common examples include motor vehicles for personal use and certain employee-benefit expenses). Don't assume every GST amount paid is automatically recoverable as credit.

How to Read This Calculator's Four Result Fields

The tool above always shows a base amount and a tax figure, but which one you treat as your "given" number depends on the type you selected. In exclusive mode, the amount you typed is the base, and CGST/SGST or IGST get added to arrive at the total. In inclusive mode, the amount you typed is the total, and the tool solves backward for the base — dividing by (1 + rate) rather than multiplying — so the base amount shown is smaller than what you entered, not larger.

A quick way to sanity-check any inclusive calculation: multiply the extracted base amount by the rate and confirm it lands close to the displayed tax component, and confirm base plus tax reproduces your original inclusive figure. If those two checks don't roughly match, re-verify the rate you selected rather than the arithmetic — a wrong rate is the most common source of a number that "looks off."

Why Businesses Care About the Intra-State vs Inter-State Split

The CGST/SGST vs IGST distinction isn't just a labeling exercise for the invoice — it determines which government account the tax lands in, and it affects how ITC can be used. Broadly, credit of IGST can be used to set off CGST, SGST, or further IGST liability, while CGST credit can only be used against CGST or IGST liability (never against SGST), and SGST credit works the mirror way. Getting the classification wrong on an invoice — charging CGST+SGST for what was actually an inter-state supply, or vice versa — is a common compliance error that can require correction and, in some cases, attracts separate liability for the wrong tax head even after the correct one is eventually paid.

For most day-to-day billing, the place of supply rules determine which category a transaction falls into: for goods, it's usually the location where the goods are delivered; for services, the rules vary more by service type. When in doubt on a transaction that doesn't fit the simple "buyer's state differs from seller's state" pattern, treat the place-of-supply determination as a separate check before relying on this calculator's split.

GST on Price Reductions and Free Supplies

GST is generally computed on the transaction value actually charged — a price reduction given before or at the time of supply, and recorded on the invoice, lowers the taxable value before GST is applied, rather than GST being charged on the pre-reduction price and refunded later. A price reduction agreed after the sale can also lower taxable value, but only if it was agreed in advance under the original supply agreement and is linked to specific invoices through a credit note. This calculator works off the final transaction value you enter — if you're quoting a price before a reduction is applied, run the calculation on the final, reduced figure to get an accurate tax number.

Rounding and Invoice-Level Precision

Real invoices round each line's tax to the nearest rupee (or paisa, depending on the business's convention) rather than rounding only the final total — on multi-line invoices, the sum of individually-rounded line taxes can differ by a rupee or two from a single tax calculated on the invoice grand total. This calculator computes tax on a single amount, so treat its output as accurate for that one line item; for a full multi-line invoice, your accounting or billing software will apply its own line-by-line rounding convention, and small rupee-level differences from a manual back-of-envelope check are normal rather than a sign of an error.

Reverse Charge: When the Buyer Pays GST Instead of the Seller

For a specific, notified list of goods and services, the liability to pay GST shifts from the supplier to the recipient of the supply — this is called reverse charge, and it's the opposite of the usual arrangement this calculator assumes (where the seller collects and remits GST). Common examples include certain services received from an unregistered supplier or specific categories notified by the government from time to time. Under reverse charge, the recipient pays GST directly to the government rather than to the supplier, and can typically claim it back as Input Tax Credit if otherwise eligible, subject to the usual ITC conditions. Since the list of reverse-charge categories is periodically updated and isn't limited to any one industry, check whether a specific purchase falls under reverse charge before assuming the standard forward-charge treatment this calculator models applies to it.

Composite and Mixed Supplies: When One Invoice Has More Than One Rate

Real transactions don't always fit a single GST rate cleanly. A composite supply — two or more items naturally bundled together in the ordinary course of business, where one is clearly the main supply and the rest incidental to it (a classic example is goods sold along with their transport and insurance as one package) — is taxed entirely at the rate applicable to that main, "principal" supply, rather than splitting the invoice across multiple rates. A mixed supply — items bundled together for a single price but not naturally tied to each other, such as a gift hamper combining unrelated products — is instead taxed at the highest rate applicable to any item in the bundle. This calculator computes tax on a single rate you select; if you're invoicing a bundled supply, work out first whether it's composite or mixed and apply the correct single rate accordingly, rather than running each component through this tool separately.