GST Calculator

Add GST on top of a base amount, or pull GST out of a GST-inclusive price. Splits CGST/SGST or IGST automatically.

How GST is calculated

When the price you have is before tax (GST-exclusive), GST = amount × rate ÷ 100 and the total is amount + GST. For example, ₹10,000 at 18% gives GST of ₹1,800 and a total of ₹11,800.

When the price already includes GST, the taxable value = total × 100 ÷ (100 + rate) and GST = total − taxable value. For example, ₹11,800 at 18% backs out to a taxable value of ₹10,000 and GST of ₹1,800.

CGST + SGST or IGST?

A sale within one state is split equally into CGST (central) and SGST (state or union territory). At 18% that is 9% CGST + 9% SGST. A sale between two states carries a single IGST at the full rate (18% IGST).

Which GST rate should I use?

The rate depends on the goods or service, identified by its HSN or SAC code. After the GST 2.0 changes effective 22 September 2025, most items sit at 5% or 18%, with 0% for exempt items and 40% for a short list of sin and luxury goods. A few items, such as precious metals, have special rates. Use the HSN / SAC rate finder to look up a code, and always confirm against the official CBIC rate schedule before you invoice.

Frequently asked questions

Is this GST calculator free?: Yes. It is free, unlimited and needs no sign-up. All maths runs in your browser and nothing you type is sent to a server.
How do I remove GST from a total price?: Choose Remove GST, enter the GST-inclusive amount and pick the rate. The calculator shows the taxable value and the GST that was inside the price.
Can I use these figures on a tax invoice?: Use them as a quick check. Real invoices should come from your accounting software, because filing-grade GST rounding and place-of-supply rules are applied there.