Reverse GST Calculator — Extract Base Price from GST-Inclusive Amount
Extract base amount and GST from tax-inclusive prices. Get instant CGST/SGST or IGST breakdown for all GST rates.
Enter Details
Older rates (before 22 Sep 2025)
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
Pick the current GST rate (5%, 18% or 40%), or an older rate (12%/28%) for a pre-Sep-2025 invoice
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 |
| ₹1,18,000 | 18% | ₹1,00,000 | ₹18,000 | ₹9,000 | ₹9,000 |
| ₹1,40,000 | 40% | ₹1,00,000 | ₹40,000 | ₹20,000 | ₹20,000 |
| ₹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.
Frequently Asked Questions
What is Reverse GST Calculation?
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.
How to calculate GST amount from inclusive price?
To calculate GST from an inclusive price: First find the base amount using Base = Inclusive × 100 ÷ (100 + Rate). Then GST Amount = Inclusive Amount - Base Amount. For 18% GST on ₹1,180: Base = 1180 × 100 ÷ 118 = ₹1,000, GST = 1180 - 1000 = ₹180.
What is the formula for reverse GST calculation?
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.
When do I need reverse GST calculation?
Reverse GST calculation is needed when: 1) You receive an invoice showing only the total amount without GST breakdown, 2) You need to claim Input Tax Credit and must know the exact GST paid, 3) You're preparing accounts and need to separate base value from GST, 4) You're verifying invoice calculations from suppliers.
What is the difference between CGST+SGST and IGST in reverse calculation?
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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