Reverse GST Calculation: Extract GST From a Total Price
Last updated: 2 July 2026 · 5 min read
Sometimes you know the final, tax-inclusive price and need to work backwards to the base value and the GST inside it — for example to record the taxable value in your books. That is a reverse GST calculation.
The formula
Base amount = Inclusive price × 100 ÷ (100 + Rate), and GST included = Inclusive price − Base amount.
Worked examples
| Inclusive price | Rate | Base | GST included |
|---|---|---|---|
| ₹1,180 | 18% | ₹1,000.00 | ₹180.00 |
| ₹525 | 5% | ₹500.00 | ₹25.00 |
| ₹1,400 | 40% | ₹1,000.00 | ₹400.00 |
Splitting the extracted GST
Once you have the GST portion, split it the same way as a forward calculation: CGST + SGST for intra-state, or IGST for inter-state. The reverse GST calculator does this instantly.
FAQ
How do I reverse-calculate GST?
Base = inclusive × 100 ÷ (100 + rate); the GST is the difference. ₹1,180 at 18% → base ₹1,000, GST ₹180.
Related: how to calculate GST, reverse GST calculator, inclusive GST calculator.
For informational purposes only. Verify with the official GST portal or a qualified tax professional.