GST formulas
Adding GST to a price that doesn't include tax:
Gross price = Net price + GST
Removing GST from a price that already includes tax (for example an MRP or a total on a bill):
GST = Gross price − Net price
Example: a laptop bag priced at ₹1,180 including 18% GST has a net price of ₹1,180 × 100 ÷ 118 = ₹1,000, and GST of ₹180 — split as ₹90 CGST and ₹90 SGST if sold within the same state.
CGST, SGST and IGST
- Intra-state sale (seller and buyer in the same state): the GST is split equally into CGST (central) and SGST (state) — or UTGST in union territories.
- Inter-state sale (different states, and imports): the full GST is charged as IGST.
GST rate slabs after GST 2.0
From 22 September 2025 the GST Council simplified most goods and services into two main slabs — 5% (merit rate) and 18% (standard rate) — plus a 40% rate for luxury and "sin" goods. Special rates continue for some items, such as 3% on gold and silver and 0.25% on rough diamonds, and many essentials are exempt (0%). Some 12% and 28% rates may still appear on older invoices or specific items, so the calculator keeps those options.
GST rates change through GST Council notifications. Always confirm the current rate for your HSN/SAC code on the official GST portal or with your tax adviser.
Who uses a GST calculator?
- Shopkeepers and freelancers preparing quotations and invoices.
- Buyers checking how much tax is included in a price.
- Accountants reconciling input tax credit.
Frequently asked questions
How do I calculate GST from a total amount?
Divide the total by (1 + rate ÷ 100) to get the net price, then subtract it from the total. For 18% GST on ₹1,180: 1,180 ÷ 1.18 = ₹1,000 net, so GST is ₹180.
What are the current GST rates in India?
Since 22 September 2025, most items are taxed at 5% or 18%, with 40% for luxury and sin goods, and special rates like 3% for gold. Check the GST portal for your item's rate.
When do I charge IGST instead of CGST and SGST?
Charge IGST when goods or services are supplied from one state to another (or imported). Charge CGST + SGST when the supplier and the place of supply are in the same state.
Is GST charged on MRP?
MRP in India already includes all taxes. Use "Remove GST" to see how much of the MRP is tax.