The GST Calculator is a free online utility that helps individuals, businesses, accountants and finance teams instantly compute the Goods and Services Tax on any transaction. Whether you need to add GST to a base price or extract the tax portion from a GST-inclusive amount, this tool delivers accurate results in seconds and clearly separates the CGST, SGST and IGST components based on the type of supply.
India moved to a unified indirect-tax structure on 1 July 2017, replacing a maze of central and state taxes with a single Goods and Services Tax. Even though the concept is simple, real-world calculations quickly become tricky when you have to decide between intra-state and inter-state rates, apply reverse-charge, or reconcile invoices at different rates. This calculator removes that guesswork with a clean interface and instant math.
What is GST and how is it calculated?
Goods and Services Tax (GST) is a destination-based, multi-stage, comprehensive indirect tax levied on the supply of goods and services in India. It is charged at every stage of the value chain, with input-tax credit available at each step so that the ultimate burden rests only on the final consumer.
The GST payable on any transaction is arrived at by applying the notified rate to the taxable (assessable) value of the supply. The taxable value is generally the transaction value — the price actually paid or payable — after adjusting for discounts, but excluding the GST itself.
- GST amount = Taxable Value × GST Rate ÷ 100
- GST-inclusive price = Taxable Value × (1 + GST Rate ÷ 100)
- Extracted GST from a total = Total × Rate ÷ (100 + Rate)
- Base value from an inclusive total = Total × 100 ÷ (100 + Rate)
CGST, SGST, UTGST and IGST — how the split works
GST in India is a dual-tax structure. On a single invoice the total GST rate is either split between the Centre and the State (or Union Territory) or charged entirely as an integrated tax, depending on the place of supply.
Intra-state supplies (CGST + SGST/UTGST)
When the supplier and the place of supply are in the same state or union territory, the tax is split equally between the Central Government (CGST) and the State Government (SGST) or Union Territory (UTGST).
- A 5% intra-state supply → 2.5% CGST + 2.5% SGST
- A 12% intra-state supply → 6% CGST + 6% SGST
- A 18% intra-state supply → 9% CGST + 9% SGST
- A 28% intra-state supply → 14% CGST + 14% SGST
Inter-state supplies (IGST)
When the supplier and the recipient (place of supply) are in different states or when goods are imported into India, a single Integrated GST (IGST) applies. IGST is collected by the Centre and later apportioned to the destination state.
- A 18% inter-state supply → 18% IGST (no state split on the invoice)
- IGST is also the rate applied on imports, in addition to Basic Customs Duty and other levies
How to use this GST Calculator
The tool is designed to be operated in a few clicks with no signup and no data leaving your browser. Follow these steps for both directions of calculation.
- Step 1Enter the amount in INR — this is the base amount if you are adding GST, or the total amount if you are extracting GST.
- Step 2Pick the applicable GST slab: 0%, 5%, 12%, 18% or 28%.
- Step 3Choose the mode — "Add GST" or "Remove GST" — depending on whether the entered amount is exclusive or inclusive of tax.
- Step 4Toggle the "Intra-state" checkbox to switch between CGST + SGST and IGST-only display.
- Step 5Read the computed base value, GST amount, tax split and gross total on the right panel.
When should you use each calculation mode?
Add GST (forward calculation)
Use forward calculation when you have a pre-tax price list or a quotation and need to raise a tax invoice. This is the most common use case for sellers, freelancers and manufacturers.
Remove GST (reverse calculation)
Use reverse calculation when you have a bill or a MRP that already includes GST and you need to separate the tax component — for example, when booking a purchase in the books of account, claiming input-tax credit, or reimbursing an employee.
Who benefits from this calculator?
- Small business owners raising tax invoices in Excel or Tally
- Freelancers and consultants issuing service invoices under GST
- E-commerce sellers calculating GST-inclusive listing prices
- Accountants reconciling GSTR-1, GSTR-3B and books of accounts
- Importers verifying the IGST component of a bill of entry
- Students of taxation, CA / CS / CMA aspirants and finance interns
- Customers who want to verify the tax portion on any bill they receive
Common mistakes to avoid
- Applying CGST + SGST on an inter-state invoice or vice-versa — always verify the place of supply
- Forgetting to add GST cess on notified goods such as tobacco, aerated drinks, coal and certain motor vehicles
- Rounding the tax at line-item level instead of at the invoice level as required by rules
- Using the wrong HSN or SAC code and consequently the wrong rate — cross-check with our HSN Lookup tool
- Charging GST on exempt supplies or on transactions outside the scope of GST