Use this free online GST calculator to quickly add GST to a base amount or remove GST from a GST-inclusive amount. It also splits the tax into CGST and SGST, making it handy for invoicing and quick tax checks under India's GST system.
How to Use the GST Calculator
Enter the "Amount (₹)" you want to calculate GST on.
Pick a preset "GST Rate (%)" (5%, 12%, 18%, or 28%) or type a custom rate in the field below it.
Choose the "GST Mode": "Add GST to amount" if your amount excludes tax, or "Remove GST from amount" if it's GST-inclusive.
Click "Calculate GST" to see the base amount, GST amount, CGST/SGST split, and total amount.
Frequently Asked Questions
"Add GST" treats your entered amount as the base (tax-exclusive) price and calculates GST = base × rate / 100 on top of it. "Remove GST" treats your amount as tax-inclusive and works backward using base = total / (1 + rate/100) to extract the base price and GST portion.
The calculator splits the total GST amount equally in half — CGST and SGST each equal GST ÷ 2 — which reflects how intra-state GST is typically divided between central and state tax in India.
You can quickly select the common slabs of 5%, 12%, 18%, or 28% from the dropdown, or type any custom rate of zero or higher into the rate field for other tax scenarios.
The amount must be greater than zero and the GST rate must be zero or positive. Otherwise, the calculator displays "Invalid input!" instead of a result. This GST calculator is completely free to use.