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Reverse GST Calculator

The pre-tax value inside a GST-inclusive price. Divide by one plus the rate; subtracting the rate from the total is the common error and lands short every time.

Also called: reverse gst, gst backward calculation, extract gst from total.

₹
That amount is
Type of supply
Total including GST
₹11,800

₹10,000 before tax plus ₹1,800 of GST gives ₹11,800. Within one state, so it splits equally into CGST and SGST.

Taxable value
₹10,000
GST
₹1,800
CGST
₹900
SGST
₹900
IGST
₹0
How it splits
Within one state, so it splits equally into CGST and SGST.
How this is calculated

Computed from the published rates for the tax year you selected, which is not necessarily the current year. A calculation, not tax advice, and it does not know anything about your circumstances beyond the figures entered.

Method and background

This is what the calculation gives for the numbers you entered. It is an estimate, not advice, and it knows nothing about your situation beyond those numbers. Rules for India change on a published schedule; the effective date is shown on every rule-based tool.

How this is calculated

A price on a shelf or an invoice total already contains the tax. Recovering the taxable value means dividing by one plus the rate, because the tax was computed on the smaller number. At 18% the divisor is 1.18, and the difference between dividing and subtracting on a ₹1,180 total is ₹32.40.

from a tax-inclusive price: net = gross / (1 + rate); tax = gross - net
G
The tax-inclusive amount (currency)
r
The GST rate (decimal)

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

1,180 inclusive at 18% is 1,000 plus 180

Amount
₹1,180
GST rate
18%
That amount is
Amount already includes tax
Type of supply
Within the state (CGST + SGST)

Total including GST₹1,180

Exact division; the figure most often got wrong by subtraction

Open this example

at 5% the divisor is 1.05

Amount
₹1,050
GST rate
5%
That amount is
Amount already includes tax
Type of supply
Within the state (CGST + SGST)

Total including GST₹1,050

arithmetic identity

Open this example

an exempt total has nothing to extract

Amount
₹1,000
GST rate
Exempt (0%)
That amount is
Amount already includes tax
Type of supply
Within the state (CGST + SGST)

Total including GST₹1,000

degenerate case

Open this example

Method and limits

What it assumes

  • The rate entered is the rate applying to the supply. Classification is a legal question this calculator does not answer.

What it deliberately does not model

  • Compensation cess on tobacco, aerated drinks and some vehicles is charged over and above GST and is not included.
  • Reverse charge, composition scheme and input credit are separate mechanisms.

Sources

Formula version 1.0.0 · definition 1.0.0 · India · Report a problem with this calculator

Frequently asked questions

Why can I not just subtract 18% from the total?
Because the 18% was charged on the pre-tax price, not on the total. Subtracting takes 18% of the larger number and lands short. Dividing by 1.18 recovers the price the tax was actually calculated on.
What is the difference between CGST, SGST and IGST?
They are the same money split differently. A supply inside one state splits the rate equally between the centre and the state; a supply between states is collected as one integrated tax and apportioned afterwards. The total the customer pays is identical.