How to Calculate GST in India (Simple 2026 Guide)

GST (Goods and Services Tax) is India's unified indirect tax. Whether you're billing a customer or checking a price, here's how to calculate it correctly.

How to ADD GST to a price

GST amount = Base price × GST rate ÷ 100. Total = Base price + GST.

Example: a product priced at ₹1,000 with 18% GST → GST = ₹180, total = ₹1,180.

How to REMOVE GST from a total

If a price already includes GST, the base = Total ÷ (1 + rate ÷ 100).

Example: ₹1,180 inclusive of 18% GST → base = 1180 ÷ 1.18 = ₹1,000, so GST = ₹180.

CGST vs SGST vs IGST

• Within the same state: GST splits equally into CGST (central) and SGST (state). For 18%, that's 9% + 9%.
• Between states: a single IGST applies at the full rate.

The common GST slabs

Most goods and services fall under 5%, 12%, 18% or 28%. Essentials are taxed lower; luxury and "sin" goods higher.

Calculate it instantly

Skip the maths — our free GST Calculator adds or removes GST at any slab and shows the CGST + SGST split. Running a business? Pair it with our Discount Calculator.