GST Calculator: Inclusive and Exclusive Amounts
Work out GST in either direction: add it to a pre-tax amount, or extract it from a price that already includes GST. Results are split into CGST and SGST/UTGST for supplies within a state, or shown as IGST for supplies between states.
How to calculate GST
- Choose "Add GST" if your amount excludes tax, or "Remove GST" if it already includes tax.
- Enter the amount and type the GST rate, or tap one of the common slab buttons.
- Pick "Within a state" for a CGST + SGST split, or "Between states" for IGST.
- Read the breakdown and copy it if you need it in an invoice or email.
Why you can't remove GST by subtracting the rate
If a price of 1,180 includes 18% GST, the tax is not 18% of 1,180 (212.40). The 18% was charged on the pre-tax amount, so the net amount is 1,180 × 100 ÷ 118 = 1,000 and the GST is 180. The "Remove GST" mode uses this reverse formula. For general percentage questions, see the Percentage Calculator.
Benefits
- Works in both directions with the correct reverse formula for inclusive prices.
- Shows the CGST/SGST split or IGST for the type of supply you choose.
- The custom rate field takes any rate, so rate changes don't break the tool.
Limitations
- Doesn't know which rate applies to a product or service. Slab buttons are common rates only, and India rationalised its GST rates in 2025, so always check the current notification.
- Cess, reverse-charge rules and invoice-level rounding are not applied.
Privacy and security
Every number you type is calculated by JavaScript in this browser tab. Nothing is sent to a server or saved after you close the page.
Read our privacy policy for details about the site as a whole.
Frequently asked questions
How do I calculate GST on an amount?
Multiply the pre-tax amount by the rate and divide by 100. At 18%, GST on 1,000 is 180 and the total is 1,180.
When is CGST + SGST charged instead of IGST?
When the supplier and the place of supply are in the same state or union territory, the tax is split equally into CGST and SGST (or UTGST). When they are in different states, the whole amount is charged as IGST.
Are the slab buttons the current legal rates?
Not necessarily. They are quick-fill values for commonly used slabs. Rates are revised by the GST Council (most recently in a 2025 rationalisation), so confirm the rate for your item and type it in the custom field if needed.