GST Calculator India: Complete Guide with Formulas (2026)

What is GST?

Goods and Services Tax (GST) is India's single indirect tax introduced in 2017. It replaced multiple taxes like VAT, service tax, and excise duty.

GST Slabs in India (2026)

• 0% — Essential items (milk, vegetables, books)
• 5% — Mass-consumption goods (sugar, tea, edible oils)
• 12% — Processed foods, mobile phones
• 18% — Most products and services
• 28% — Luxury items (cars, AC, washing machines)

GST Calculation Formulas

1. Add GST to base price (Exclusive)

Formula: Final Price = Base Price + (Base Price × GST% / 100)

Example: Product costs Rs 1,000. Add 18% GST.
GST Amount = 1,000 × 18 / 100 = Rs 180
Final Price = 1,000 + 180 = Rs 1,180

2. Extract GST from total price (Inclusive)

Formula: Base Price = Total Price × 100 / (100 + GST%)

Example: Total bill is Rs 1,180 (incl. 18% GST).
Base = 1,180 × 100 / 118 = Rs 1,000

CGST + SGST vs IGST

Intra-state sale: GST splits equally into CGST + SGST. For 18%: CGST 9% + SGST 9%.

Inter-state sale: Full GST goes as IGST. For 18%: IGST 18%.

Use Our Free Calculator

Skip the manual math. Use our free GST Calculator for all four slabs and CGST/SGST/IGST splits.