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GST calculation: CGST, SGST and IGST explained
Within a state, GST is split equally into CGST and SGST (18% becomes 9% + 9%). Between states, the whole GST is charged as IGST. To add GST, multiply the price by (1 + rate). To remove it from an inclusive price, divide by (1 + rate).
Add GST to a price
₹1,000 at 18% GST: GST = 1,000 × 18% = ₹180; total ₹1,180. Within a state that's CGST ₹90 + SGST ₹90.
Remove GST from a GST-inclusive price
₹1,180 including 18% GST: base = 1,180 ÷ 1.18 = ₹1,000; GST = ₹180.
₹1,050 including 5% GST: base = 1,050 ÷ 1.05 = ₹1,000; GST = ₹50 (CGST ₹25 + SGST ₹25).
CGST + SGST or IGST?
- Same state (intra-state): CGST + SGST, each half the rate.
- Different states (inter-state): IGST at the full rate.
Which rate applies?
Rates depend on the goods or service and were restructured in September 2025. Check the current rate for your item with your accountant or the official GST portal before billing.
Calcsend's GST calculator adds or removes GST and shows the CGST/SGST split, alongside its EMI, SIP and site calculators.