This GST Calculator helps you add GST to a price, or work backwards from a GST-inclusive total to find the original price and the tax in it. It also shows the CGST and SGST split for sales within a state, or the IGST amount for sales between states.
How to use the GST Calculator
- Choose whether to add GST to a price or remove GST from a total.
- Enter the amount in rupees.
- Select the GST rate, or choose “Other rate” and type your own.
- Choose same-state (CGST + SGST) or different-state (IGST) supply.
- Select Calculate GST to see the price before tax, the GST amount and the total.
GST formulas explained
To add GST: GST amount = price × rate ÷ 100, and total = price + GST amount.
To remove GST: price before GST = total × 100 ÷ (100 + rate), and GST amount = total − price before GST.
For sales within a state, the GST is split equally between CGST (central) and SGST (state). For sales between states, the full amount is charged as IGST.
Worked examples
Adding GST: a service priced at ₹1,000 with 18% GST has GST of ₹180, so the total is ₹1,180. Within a state, that is ₹90 CGST and ₹90 SGST.
Removing GST: a bill totals ₹1,180 including 18% GST. The price before GST is 1,180 × 100 ÷ 118 = ₹1,000, and the GST is ₹180. Note that taking 18% of ₹1,180 would give ₹212.40, which is wrong, because the 18% was charged on the smaller original price.
For a step by step explanation, read our guide How to Calculate GST.
What this calculator does not include
The calculator applies one rate to one amount. It does not decide which rate applies to your goods or services, and it does not handle cess, input tax credit, composition scheme rules or invoices with several items at different rates. GST rates and rules change over time, so confirm the current rate on the official GST portal or with a tax professional.
Frequently asked questions
How do I find the price before GST?
Choose “Remove GST from a total”, enter the GST-inclusive price and the rate. The calculator divides by (1 + rate ÷ 100).
What is the difference between CGST, SGST and IGST?
CGST and SGST are charged together on sales within one state, each at half the GST rate. IGST is charged on sales between states at the full rate.
Why are older rates such as 12% and 28% listed?
They are provided as “earlier slab” options so you can check older invoices. Current rates for an item should be confirmed from official sources.
Tax information: This tool gives general estimates, not tax or legal advice. Please confirm rates and rules with the GST portal or a qualified professional.