Learn before you calculate
GST Calculator: a practical India guide
Add GST to a taxable value or extract GST from an inclusive price. See the tax split for intra-state and inter-state assumptions and build a simple multi-item invoice estimate.
Educational estimates, not financial, tax or legal advice
Quick answer
For an exclusive price, GST is taxable value × rate. For an inclusive price, the tax portion is inclusive price × rate ÷ (100 + rate). Intra-state tax is generally split between CGST and SGST or UTGST; inter-state supply generally uses IGST.
How to use this calculator well
- 1Choose exclusive when GST must be added, or inclusive when the entered price already contains GST.
- 2Enter the taxable or inclusive amount exactly as described by the selected mode.
- 3Select the GST rate applicable to the specific goods or services and transaction date.
- 4Choose the inter-state assumption when IGST applies; otherwise review the CGST and SGST split.
- 5Use the result for arithmetic and confirm classification, place of supply and invoice treatment separately.
Formula and method
GST amount formulas
Exclusive: GST = Value × rate ÷ 100. Inclusive: GST = Price × rate ÷ (100 + rate)
The correct rate and tax type depend on classification, exemptions, place of supply, reverse charge and other GST provisions. The calculator does not determine those legal facts.
Adding GST and removing GST from a price
When a quoted amount is before tax, multiply the taxable value by the applicable rate and add the result. When the quoted amount already includes tax, do not simply multiply by the rate; extract the embedded tax using the inclusive-price formula.
This distinction is important in retail pricing, quotations and reconciliation. A ₹118 inclusive price at 18% contains ₹18 tax and ₹100 taxable value—it does not contain ₹21.24 tax.
CGST, SGST, UTGST and IGST
For a typical intra-state supply, the total GST rate is divided between central tax and the relevant state or union-territory tax. For a typical inter-state supply, integrated tax applies. The total percentage may be the same while the ledger split changes.
Determining place of supply can be more complex than comparing seller and buyer addresses, especially for services, e-commerce, movement of goods and special transactions. Use the calculator after the tax type has been determined.
Choosing the correct GST rate
GST rate depends on classification, notifications, exemptions and the transaction date. Similar-sounding goods or services can have different treatment. Common rate buttons improve speed but do not classify the supply for you.
For a business invoice, verify the HSN or SAC, place of supply, tax status of the parties and any cess or special treatment. Keep source documentation for the rate selected.
Invoice totals and input tax credit
A multi-item estimate helps total taxable value and output tax across lines with different rates. A valid tax invoice must still contain the particulars required under current GST rules and reflect the actual supplier, recipient and supply.
Input tax credit cannot be established by this arithmetic alone. Eligibility depends on legal conditions, documents, receipt of supply, return reporting and restrictions. Reconcile with books and the GST system.
Questions people ask
GST Calculator FAQs
Concise answers to common planning questions. Open any question for the full explanation.
How do I add 18% GST to an amount?
Multiply the taxable amount by 18 ÷ 100, then add that tax to the original amount. For ₹1,000, GST is ₹180 and the tax-inclusive total is ₹1,180.
How do I remove GST from an inclusive price?
Use inclusive price × rate ÷ (100 + rate) to find the tax portion. Subtract that tax from the inclusive price to get taxable value.
What is reverse GST calculation?
It commonly means extracting the GST amount and taxable value from a price that already includes tax. It is not necessarily the same as the legal reverse-charge mechanism.
What is the difference between CGST and SGST?
They are the central and state components generally charged together on an intra-state supply. Each receives its prescribed share of the total GST rate.
When is IGST used?
IGST generally applies to inter-state supplies and specified cross-border situations. Place-of-supply rules determine the treatment and can require professional interpretation.
Are CGST and SGST always half of the GST rate?
For many standard intra-state supplies they split the total rate equally, but legal exceptions or additional levies can exist. Verify the applicable rule.
How do I know which GST rate applies?
Identify the correct HSN or SAC and check current notifications or official guidance for the transaction date. The calculator cannot classify goods or services.
Does the calculator include GST compensation cess?
It calculates the GST fields displayed by the tool. Any applicable compensation cess or special levy must be handled separately unless explicitly provided.
Can I use this result as a GST invoice?
No. It is an arithmetic estimate. A valid tax invoice must include prescribed business, supply, tax and document particulars.
What is input tax credit?
It is eligible credit of input tax against output tax subject to GST law and documentation. A calculated GST amount does not by itself establish credit eligibility.
How is GST rounded on an invoice?
Software and invoicing policies may round at line or document level within applicable rules, producing small differences. Use a consistent method and retain the detailed calculation.
Does GST apply to every sale?
No. Registration status, exemption, zero rating, composition rules, reverse charge and the nature of supply can change treatment. Check the applicable law.