Reverse GST Calculator

When this applies

• A vendor quoted you one all-in price and you need the taxable value for your records.
• You are comparing two quotes at different rates and want the base values side by side.
• You paid a GST-inclusive bill and need to split it into expense and input tax credit.
• You are checking that a bill's arithmetic is right.

Splitting an 18% inclusive price of INR 11,800

1. 1Inclusive amount INR 11,800 at 18%.
2. 2Taxable value = 11,800 / 1.18 = INR 10,000.
3. 3GST included = 11,800 - 10,000 = INR 1,800.
4. 4Check: 10,000 x 18 / 100 = INR 1,800.

The price is INR 10,000 taxable plus INR 1,800 GST.

What this calculator does

Back-calculate the base value hidden inside a GST-inclusive price. Enter the price you were quoted or charged and the rate, and it returns the taxable value and the GST that is already sitting inside the figure.

How this is calculated

An inclusive price is the taxable value plus GST, so the taxable value is the price divided by (1 + rate / 100) and the GST is the difference. At 18%, dividing by 1.18 strips the tax back out. This is the calculation you need whenever a vendor quotes one all-in number and you have to record the base value and the tax separately.

The formula

Taxable = Total ÷ (1 + rate/100) · GST = Total − Taxable

Common mistakes to avoid

• Taking the rate off the inclusive total

  18% of INR 11,800 is INR 2,124, not the INR 1,800 actually included. The base must be divided out first.

• Reversing at the wrong rate

  A 12% inclusive price divided by 1.18 gives a wrong base. Use the rate that was actually applied.

• Assuming the rate from the price

  You cannot infer the rate from a single inclusive figure. Ask for the rate, or the tax invoice, rather than guessing it.

Frequently asked

When do I need to reverse a GST-inclusive price?

Whenever a price is quoted or paid as a single all-in figure but the base value and the tax have to be recorded separately - on a purchase, in your books, or when you compare quotes at different rates.

What is the formula?

Taxable value = inclusive price / (1 + rate / 100), and GST = inclusive price minus taxable value. At 18% on INR 11,800 the taxable value is INR 10,000 and the GST is INR 1,800.

Why is the GST not simply 18% of the inclusive price?

Because the inclusive price already contains the tax. Taking 18% of it would give you the tax on the tax. The base has to be divided out first, which is why the base is slightly less than 18% of the total.

Does the split between CGST/SGST and IGST change the base?

No. The base value and the total tax are the same whether the supply is intra-state or inter-state; only the head under which the tax is reported differs.

Is my data saved?

No. The calculation runs entirely in your browser and nothing is stored or transmitted.