View calculation formula
Base Price = Total ÷ (1 + Rate / 100)
GST Amount = Total − Base Price
Example: ₹11,800 ÷ 1.18 = ₹10,000 Base → GST ₹1,800
How to Reverse Calculate GST
Extract GST in 3 simple steps
Enter Total Amount
Input the total price including GST
Select Rate
Choose the GST rate that was applied
Get Results
View original price and extracted GST instantly
Common Mistake Alert
Don't calculate reverse GST the wrong way
Subtracting 18% directly from total:
This calculates 18% of the total amount, removing too much value.
Dividing by (1 + rate):
This extracts the original base price that 18% was added to.
Why? GST is calculated on the original price, not the total.
₹10,000 + 18% = ₹11,800. To reverse, we must divide by 1.18.
Reverse GST Formula
See how to extract GST from total
Original = Total ÷ (1 + Rate ÷ 100)
Understanding Reverse GST
The concept behind the calculation
What is it?
It’s the process of working backwards from a “Total Amount” to find the original product cost and the tax component. Essential for “Inclusive” pricing.
Why “Reverse”?
Normal math goes Base + GST = Total. Reverse math goes Total → Remove GST → Base. It requires division, not subtraction.
The Math
Tax is based on the smaller base number. We divide the total by (1 + Rate) to shrink it back to its original size perfectly.
Real-World Scenarios
When to use this calculator
Freelancers
A client pays a flat ₹50,000 fee inclusive of tax.
Retail Pricing
Selling a product at ₹999 MRP (12% GST).
Reimbursements
Reconstructing tax from a credit card charge.
Quick GST Rate Guide
Common items and their standard rates
Rate | Type | Examples |
|---|---|---|
5% | Essentials | Packaged food, Footwear (<₹1000), Apparel (<₹1000), Train tickets |
12% | Standard | Processed food, Butter, Cheese, Mobiles, Business air tickets |
18% | Services | IT services, Telecom, Dining (AC), Electronics, Furniture |
28% | Luxury | Automobiles, Cement, ACs, Gaming consoles, Sodas |
- Rates subject to GST Council updates.
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Frequently Asked Questions
Everything you need to know about reverse GST calculation
What is reverse GST calculation?
Reverse GST calculation is the mathematical process of finding the original taxable value and the tax amount from a final figure that already includes GST. It is essential when you only have the total receipt amount and need to separate the tax component for accounting or tax credit purposes.
How do I remove GST from total price?
You cannot simply subtract the percentage. Instead, use the formula: Original Price = Total Value ÷ (1 + GST Rate/100). For example, for a total of ₹11,800 with 18% GST, you calculate ₹11,800 ÷ 1.18 to get ₹10,000. Then, subtract this original price from the total to get the GST amount (₹1,800).
Why can't I just subtract 18% from the total?
This is the most common mistake! GST is calculated on the *base price*, not the *total price*. If you subtract 18% from ₹11,800, you are calculating 18% of ₹11,800, which is wrong. You need to find the value which, when increased by 18%, equals ₹11,800. This requires division, not subtraction.
What is the mathematical formula for reverse GST?
The formula is: Base Value = Total Amount / (1 + (GST Rate / 100)). Once you have the Base Value, the GST Amount = Total Amount - Base Value.
When should I use a Reverse GST Calculator?
Use it when you have a bill that only shows the final amount (MRP), when you need to back-calculate the cost of a product to fit a specific budget (e.g., 'I want to sell this for ₹500 including tax'), or when verifying if a vendor has calculated tax correctly on an inclusive invoice.
Is this different from a GST Inclusive Calculator?
Mathematically, they are identical. Both tools perform the same calculation. 'GST Inclusive' usually refers to the forward pricing strategy (setting a price that includes tax), while 'Reverse GST' refers to the accounting action of extracting tax from a receipt. We offer both to match how different users think about the problem.