How to use this GST calculator
- Choose Add GST if your amount is before tax, or Remove GST if your amount already includes GST and you want to find the base value.
- Enter the amount and pick the GST slab: 0%, 5%, 18% or 40%. For a credit note on a bill dated before 22 September 2025, pick the old 12% or 28% rate from the list.
- Pick Same state to see the CGST + SGST split, or Other state for a single IGST figure.
The formula behind it
To add GST: GST = amount × rate ÷ 100, and the total is the amount plus
that GST. To remove GST from a tax-inclusive figure:
base = amount ÷ (1 + rate ÷ 100), and the GST is the difference. For a same-state sale the
GST is split equally into CGST and SGST; for an inter-state sale the whole amount is IGST.
Tired of doing this on every bill? DAM applies the right GST rate and CGST/SGST/ IGST split automatically the moment you pick an item and a customer — then prints the invoice for you.
Let DAM do the GST math for you
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Download DAM FreeFrequently asked questions
How do I calculate GST on an amount?
To add GST, multiply the base amount by the rate. GST on ₹1,000 at 18% is ₹180, so the total is ₹1,180. To remove GST from an inclusive amount, divide by (1 + rate): ₹1,180 ÷ 1.18 = ₹1,000 base, ₹180 GST.
How is the CGST and SGST split calculated?
For a sale within the same state, GST is split equally into CGST and SGST — 18% becomes 9% + 9%. For inter-state sales the full rate is charged as a single IGST.