GST Calculator
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GST Calculator summary
Calculation schedule
Figures may be rounded for display.
Saved calculations
Saved only in this browser on this device.
GST calculator formula
Choose whether the amount is before GST or already includes GST. The two calculations are different.
To add GST: GST = base price × GST rate ÷ 100 Total price = base price + GST To remove GST: Base price = inclusive price ÷ (1 + GST rate ÷ 100) GST = inclusive price − base price Within one state: CGST = GST ÷ 2 and SGST/UTGST = GST ÷ 2 Between states: IGST = full GST
Choose the rate that legally applies to the exact goods or service and the date of supply.
The calculator can split the tax amount, but it cannot decide HSN/SAC classification or place of supply.
Example with numbers
A base price of ₹1,000 with 18% GST gives ₹180 tax and a total of ₹1,180. For an intrastate sale, that is ₹90 CGST and ₹90 SGST. Entering ₹1,180 as GST-inclusive gives the same ₹1,000 base and ₹180 GST.
What is a GST calculator?
A GST calculator finds the tax part of a price. It can add GST to an exclusive amount or take GST out of an amount that already includes tax.
It can also show CGST and SGST/UTGST for an intrastate supply, or IGST for an interstate supply.
How to use the GST calculator
- Enter the price or invoice amount.
- Choose GST exclusive to add tax, or GST inclusive to remove it.
- Enter the correct GST rate and choose intrastate or interstate.
- Calculate and check base value, tax, total and the tax-head split.
What the results mean
- Taxable value: the base amount before percentage GST and entered cess.
- GST amount: total GST at the rate entered.
- Tax split: CGST plus SGST/UTGST, or the full IGST amount.
- Invoice total: taxable value plus calculated GST and entered cess.
How this GST calculation works
Adding GST is simple multiplication. Removing GST uses division because the tax rate belongs to the smaller base price, not the larger inclusive total.
For an intrastate supply, total GST is split equally. For an interstate supply, the same total appears as IGST.
Why a GST calculator is useful
- It handles both inclusive and exclusive prices.
- It shows the base price and tax separately.
- It provides the CGST/SGST or IGST split.
- It reduces mistakes when checking a simple invoice amount.
Why an invoice may show another GST amount
Line-by-line rounding, discounts, freight, mixed supplies, reverse charge and place-of-supply rules can change an invoice.
Rates and classifications can change. The calculator cannot decide which rate or tax treatment applies to your transaction.
Sources
- GST Portal: taxpayer welcome kit and GST guidance
- GST Portal: electronic ledger tax heads
- Central Board of Indirect Taxes and Customs: GST
Rule and source review: Calculation method reviewed 31 August 2026. Users must verify the current classification, rate and place-of-supply treatment.
Disclaimer
This GST calculator performs simple percentage arithmetic. It does not classify goods or services, decide place of supply or confirm tax liability. Check the current GST rate and invoice rules, or obtain professional advice for a complex transaction.
Frequently asked questions
How do I add GST to a price?
Multiply the base price by the GST rate, divide by 100 and add the tax to the base price.
How do I remove GST from an inclusive price?
Divide the inclusive price by one plus the GST rate as a decimal. The difference is the GST amount.
What is the difference between inclusive and exclusive GST?
An exclusive price is before GST. An inclusive price already contains GST.
When are CGST and SGST shown?
They are shown for an intrastate supply. The total GST is divided equally between them.
Can this calculator choose the GST rate?
No. You must enter the correct rate after checking the current classification and rules.