How GST is calculated
Adding GST: GST = amount × rate ÷ 100, and the total = amount + GST. For ₹50,000 at 18%, GST is ₹9,000 and the invoice total is ₹59,000.
Removing GST from an inclusive amount: taxable value = amount × 100 ÷ (100 + rate). For ₹59,000 including 18% GST, the taxable value is ₹50,000 and the GST is ₹9,000.
CGST + SGST or IGST?
When the supplier and the place of supply are in the same state (intra-state), GST is split equally into CGST (central) and SGST (state) — 9% + 9% for an 18% rate. In union territories without a legislature, UTGST replaces SGST.
When they are in different states (inter-state) or the supply is an import, the whole tax is charged as IGST. Exports of services under a Letter of Undertaking (LUT) are zero-rated.
Frequently asked questions
What are the current GST rates in India?
After the GST rate rationalisation effective 22 September 2025, most goods and services fall under 5% or 18%, with a 40% rate for a small set of luxury and sin goods and special rates such as 3% and 0.25%. Older 12% and 28% slabs are kept here for invoices issued before that date. Always confirm the rate for your HSN/SAC code.
What is the GST rate for digital marketing and advertising services?
Advertising and marketing services generally fall under SAC 9983 and are taxed at 18% GST. Check your exact service classification with your tax adviser.
How do I remove GST from a total?
Divide the GST-inclusive amount by (1 + rate ÷ 100). For an 18% rate, divide by 1.18 to get the taxable value; the difference is the GST.
When do I charge IGST instead of CGST and SGST?
Charge IGST when the supplier’s state and the place of supply are different (inter-state supply). Charge CGST + SGST when both are in the same state.
Is this calculator a substitute for tax advice?
No. It does the arithmetic correctly, but which rate and place of supply apply to your transaction is a legal question — confirm with a chartered accountant.
