Reverse GST Calculator
Extract base amount and GST from tax-inclusive prices. Get instant CGST/SGST or IGST breakdown for all GST rates.
Enter Details
Formula Used:
Base = Inclusive × 100 ÷ (100 + Rate)
Calculation Results
GST Breakdown
How to Use This Calculator
Enter Amount
Enter the total amount including GST (the amount on your invoice)
Select GST Rate
Choose 5%, 12%, 18%, or 28% based on product/service
Choose Type
Intra-State (same state) or Inter-State (different states)
View Results
Get instant breakdown of base amount and GST components
Copy Results
Copy the calculation for your accounting records
Reverse GST Calculation Examples
| Inclusive Amount | GST Rate | Base Amount | GST Amount | CGST | SGST |
|---|---|---|---|---|---|
| ₹1,05,000 | 5% | ₹1,00,000 | ₹5,000 | ₹2,500 | ₹2,500 |
| ₹1,12,000 | 12% | ₹1,00,000 | ₹12,000 | ₹6,000 | ₹6,000 |
| ₹1,18,000 | 18% | ₹1,00,000 | ₹18,000 | ₹9,000 | ₹9,000 |
| ₹1,28,000 | 28% | ₹1,00,000 | ₹28,000 | ₹14,000 | ₹14,000 |
| ₹59,000 | 18% | ₹50,000 | ₹9,000 | ₹4,500 | ₹4,500 |
* For Inter-State transactions, full GST is collected as IGST instead of CGST+SGST split
Frequently Asked Questions
Reverse GST calculation is the process of extracting the base amount (before GST) and GST amount from a tax-inclusive price. The formula is: Base Amount = Inclusive Amount × 100 ÷ (100 + GST Rate). For example, if an item costs ₹1,180 inclusive of 18% GST, the base amount is ₹1,000 and GST is ₹180.
To calculate GST from an inclusive price, follow these steps:
- Find the base amount: Base = Inclusive × 100 ÷ (100 + Rate)
- Calculate GST: GST Amount = Inclusive Amount - Base Amount
For 18% GST on ₹1,180: Base = 1180 × 100 ÷ 118 = ₹1,000, GST = 1180 - 1000 = ₹180
The reverse GST calculation formula is:
- Base Amount = (Inclusive Amount × 100) ÷ (100 + GST Rate)
- GST Amount = Inclusive Amount - Base Amount
- For CGST/SGST split (intra-state): Each = GST Amount ÷ 2
- For IGST (inter-state): IGST = Full GST Amount
Reverse GST calculation is needed when:
- You receive an invoice showing only the total amount without GST breakdown
- You need to claim Input Tax Credit and must know the exact GST paid
- You're preparing accounts and need to separate base value from GST
- You're verifying invoice calculations from suppliers
- You're creating purchase entries in accounting software like TallyPrime
For Intra-State transactions (within same state), GST is split equally into CGST (Central GST) and SGST (State GST). For Inter-State transactions (between different states), the entire GST is collected as IGST (Integrated GST).
The total GST amount remains the same; only the split differs. Use CGST+SGST for local transactions and IGST for interstate sales.
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