GST Calculator
Add GST to a price, or pull the GST out of an amount that already includes it. With the CGST/SGST split, because that is the part invoices get wrong.
Why the split matters
The total is identical either way — 18% is 18%. What changes is how it is reported. A supply inside one state splits into CGST and SGST at half the rate each; a supply across state lines is a single IGST line. Put the wrong one on an invoice and your client cannot claim input credit cleanly, which is the kind of thing that gets an invoice bounced back a month later.
For services, place of supply is normally where the recipient is registered, not where you sit. A freelancer in Pune billing a registered company in Bengaluru raises IGST, even though the work happened in Maharashtra.
Extracting GST is not subtracting 18%. To strip 18% from an
inclusive amount you divide by 1.18, not multiply by 0.82. On ₹10,000 that is
a ₹274 difference — a mistake that quietly compounds across a year of
invoices.