Reverse GST Calculator
This reverse GST calculator works backwards from a GST-inclusive price to reveal the base amount and the GST hidden inside it. Enter the total you charged or paid, pick the rate, and see the pre-tax value plus the CGST/SGST or IGST breakdown — handy when a price already includes tax and you need the taxable value for your books.
How to use
- Enter the GST-inclusive total amount.
- Select the GST rate or type a custom rate.
- Choose intra-state or inter-state.
- Read the base amount and the GST included.
Reverse GST formula with example
Base amount = Inclusive amount × 100 ÷ (100 + Rate)
GST included = Inclusive amount − Base amount
Example: A bill total is ₹1,180 including 18% GST. Base = 1,180 × 100 ÷ 118 = ₹1,000. GST included = 1,180 − 1,000 = ₹180, i.e. CGST ₹90 + SGST ₹90 for an intra-state sale.
FAQ
How do I remove GST from a total price?
Base = inclusive amount × 100 ÷ (100 + rate); the GST is the difference. For ₹1,180 at 18%, base = ₹1,000 and GST = ₹180.
What is a reverse GST calculation?
It works from a price that already includes GST to find the pre-tax base amount and the GST portion inside it.
Is this different from the normal GST calculator?
Yes. The normal calculator adds GST to a base price; this one extracts GST already contained in a total.
Related tools
GST Calculator
Add GST to a base amount.
Inclusive GST
Two-way converter.
GST Bill Generator
Create a full invoice.
Guide: Reverse GST
Step-by-step explanation.
Guide: How to calculate GST
Formulas and examples.
Late Fee Calculator
GSTR-3B / GSTR-1 late fees.
Last updated: 2 July 2026. GST slabs per the 56th GST Council meeting (effective 22 September 2025).