Add GST to a price you're about to invoice, or extract the GST already included in a price — with the CGST/SGST split shown.
In 'Add GST' mode, your entered amount is treated as the base price and GST is added on top. In 'Extract GST' mode, your entered amount is treated as already including GST, and the calculator backs out the base price and GST portion from that total.
For intra-state sales in India, GST splits evenly into CGST (central) and SGST (state) — shown here as half each. For inter-state sales, the full amount is charged as IGST instead of split, but the total GST amount is the same either way.
Adding 18% GST to a $1,000 invoice: GST amount is $180 ($90 CGST + $90 SGST), for a total of $1,180. Extracting GST from a $1,180 GST-inclusive amount at 18% gives the same result in reverse: base $1,000, GST $180.
Is this specific to India's GST? The CGST/SGST split is specific to India's GST system, but the core add/extract math works for any percentage-based goods and services tax — just adjust the rate and ignore the CGST/SGST breakdown if it doesn't apply to your country.
What rate should I use? India's GST has multiple slabs (commonly 5%, 12%, 18%, 28%) depending on the goods or service category — confirm the correct slab for what you're invoicing before using this for an actual invoice.
Is this tax advice? No — this is a calculation tool only, not tax advice. Confirm your specific GST obligations and correct rate with a tax professional or your local GST portal.