Reverse GST calculator

Enter a GST-inclusive total to find the base price and the GST already included, with the CGST / SGST / IGST split.

Amount

Amount (including GST)

GST rate

Inter-state (IGST)

₹1,180

total (GST included) at 18% GST

Base amount	₹1,000
CGST @ 9%	₹90
SGST @ 9%	₹90
Total GST	₹180
Total amount	₹1,180

CGST and SGST apply within a state and are each half of the GST rate; IGST applies to inter-state supply and equals the full rate. This is a calculator, not tax advice.

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What a reverse GST calculation does

A reverse (or 'remove GST') calculation starts from a price that already includes GST and finds two things: the original base price, and how much of the total was tax. It is the opposite of adding GST on top of a base amount.

The formula is base = total / (1 + rate / 100), and GST = total - base. For an Rs 1,180 amount at 18%, the base is Rs 1,000 and the GST included is Rs 180.

Worked examples

Rs 1,180 inclusive at 18% gives a base of Rs 1,000 and Rs 180 GST (CGST Rs 90 + SGST Rs 90 intra-state, or IGST Rs 180 inter-state).

Rs 1,050 inclusive at 5% gives a base of Rs 1,000 and Rs 50 GST.

Rs 1,120 inclusive at 12% gives a base of Rs 1,000 and Rs 120 GST.

When you need it

Use a reverse calculation when a quoted or MRP price is 'GST inclusive' and you need the pre-tax value - for accounting entries, input-tax-credit records, or checking a supplier's invoice. This tool also shows the CGST/SGST or IGST split so it matches how the tax appears on the invoice.

Adding GST instead? Use the GST calculator · Official GST rates (CBIC)

Questions, answered.

What is reverse GST?+

Reverse GST, also called removing GST, means working backwards from a GST-inclusive price to find the original base amount and the tax it contains, rather than adding GST on top of a base figure.

What is the reverse GST formula?+

base = total / (1 + rate / 100), and GST = total - base. For an Rs 1,180 total at 18%, the base is Rs 1,000 and the GST is Rs 180.

How do I find the base price from a GST-inclusive amount?+

Enter the inclusive total and the rate; the calculator divides by 1 plus the rate to give the base price, and shows the GST that was already included.

Does it show the CGST, SGST and IGST split?+

Yes. It splits the extracted GST into CGST and SGST (half each) for an intra-state supply, or shows a single IGST line for an inter-state supply.

Is anything I enter sent to a server?+

No. The calculator runs entirely in your browser; nothing you type is sent anywhere.

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