Reverse GST Calculator — find the tax inside a price
Many bills, MRPs and expense receipts show only the final amount paid. To record the expense correctly or claim input tax credit you need the taxable value and the GST portion separately. The Reverse GST Calculator does this back-calculation instantly: enter the inclusive amount, pick the GST rate and it returns the pre-tax value, the GST, and the CGST/SGST or IGST split.
Formula
- Taxable value = Inclusive amount × 100 ÷ (100 + GST rate)
- GST amount = Inclusive amount − Taxable value
- CGST = SGST = GST ÷ 2 for intra-state; IGST = GST for inter-state
Worked example
You paid ₹11,800 for office furniture and the bill says "inclusive of 18% GST". Taxable value = 11,800 × 100 ÷ 118 = ₹10,000. GST = ₹1,800, i.e. CGST ₹900 + SGST ₹900. Note that the GST is 18% of the taxable value but only 15.25% of the inclusive price — a common source of error when people simply take 18% of the total.
Why the comparison table helps
When you are unsure which slab a product falls under, tick "show all rates" to see the same inclusive amount split at 5%, 12%, 18%, 28% and 40%. This is handy for reconciling supplier invoices, checking whether a restaurant or hotel bill applied the right rate, or preparing a purchase register from retail receipts.
Typical uses
- Booking expenses from petrol-pump, hotel and e-commerce receipts
- Pricing products for marketplaces that require an MRP inclusive of GST
- Verifying ITC amounts in GSTR-2B against physical invoices
- Working out the net fee from an all-inclusive professional charge
Inter-state receipts
If the supplier is in another state, the whole GST portion is IGST rather than CGST plus SGST. Select "Inter-state" to see the figure under the right head, which matters when you post the entry to separate IGST, CGST and SGST input ledgers in Tally or your accounting software. Posting IGST under CGST/SGST by mistake creates a mismatch with GSTR-2B that is tedious to reverse later.
The calculator remembers your last inputs in the browser, so repetitive data entry during month-end closing is quicker.
Frequently Asked Questions
Is reverse GST the same as 18% of the total?
No. 18% of an inclusive total overstates the tax. Divide by 1.18 to get the taxable value first; the GST is the difference.
Can I claim ITC on an inclusive retail bill?
Only if the bill is a valid tax invoice showing the supplier GSTIN, your GSTIN and the tax amount, and it appears in your GSTR-2B. A plain retail receipt generally does not qualify.
How do I back-calculate GST at 5%?
Taxable value = amount ÷ 1.05. For ₹2,100 that gives ₹2,000 taxable and ₹100 GST.
Disclaimer: This tool is for general information and estimation only. Tax rates and rules change — verify with official sources or a professional before acting. Read full disclaimer.