GST-exclusive means tax is added to the base price. GST-inclusive means tax is already in the total. At an illustrative 18% rate, ₹10,000 before GST becomes ₹11,800 including GST; ₹11,800 including GST contains ₹1,800 tax and a ₹10,000 base.
Adding GST to a price
Start with an amount before GST and multiply it by the applicable rate divided by 100. Add that tax amount to the base to get the total. For a ₹10,000 base at 18%, tax is ₹10,000 × 18 ÷ 100 = ₹1,800, so the total is ₹11,800.
A quotation should make the tax basis explicit. “₹10,000 plus applicable GST” and “₹10,000 including GST” describe different commercial outcomes. Before sending a quote, decide which amount is your intended base price and confirm that the rate is appropriate for the supply. The 18% used here is a mathematical example, not a rate recommendation.
Removing GST from a total
Divide the tax-inclusive total by 1 plus the rate expressed as a decimal. At 18%, that means dividing by 1.18. Subtract the resulting base from the original total to find the tax. CBIC’s rule 35 sets out the calculation of tax contained within a tax-inclusive value.
Swipe across to see the full comparison.
| Example at 18% | Base amount | GST amount | Total |
|---|---|---|---|
| Add tax to ₹10,000 | ₹10,000 | ₹1,800 | ₹11,800 |
| Extract tax from ₹11,800 | ₹10,000 | ₹1,800 | ₹11,800 |
| Extract tax from ₹10,000 | ₹8,474.58 | ₹1,525.42 | ₹10,000 |
Do not subtract 18% of the total to remove 18% GST. That would use the wrong denominator: the rate applies to the base amount.
CBIC: CGST Rules, rule 35 (tax-inclusive value)Show the tax components separately
The calculator lets you select CGST with SGST, CGST with UTGST, or IGST. For a selected combined 18% rate and a base of ₹10,000, the paired split is ₹900 and ₹900, or ₹1,800 as IGST. Select the applicable treatment after reviewing the place-of-supply rules for the transaction.
A correct multiplication does not establish the correct legal tax treatment. Classification, exemptions, mixed rates, reverse charge and cess require their own checks. The tool handles a single entered rate and excludes cess; it is designed to check the arithmetic in a quote or price.
Check the price before using it
For several line items with different rates, calculate them separately rather than applying one average rate to the entire invoice. Save the assumptions alongside the result so another person can see how you reached the number.
- Confirm whether the amount entered includes or excludes tax.
- Use the applicable GST rate, not the calculator’s example default.
- Select the appropriate tax components for the supply.
- Compare base, tax and total with the quote or invoice.
- Review invoice rounding and any items that need separate treatment.
Common questions.
How do I remove 18% GST from ₹11,800?
Divide ₹11,800 by 1.18 to get ₹10,000 before GST. The difference, ₹1,800, is the included tax.
Is reverse calculation the same as reverse charge?
No. Extracting tax from an inclusive price is arithmetic. Reverse charge is a legal mechanism that changes who is liable to pay GST.
Does the GST calculator tell me my filing liability?
No. It shows price and tax arithmetic for the rate entered. Filing liability also depends on the applicable rules and records.
Official references.
Sources checked for this edition on 9 October 2026. Portal instructions and requirements can change.
General information and preparation guidance. Confirm the requirements and treatment that apply to your circumstances. This article does not make a filing or registration decision for you.
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