Work backwards from a GST-included price to find the price before tax.
Divides the inclusive price back out to recover the pre-tax value.
Taxable value: Inclusive price × 100 ÷ (100 + rate)
Most price tags in Indian shops show one figure, and GST is already inside it. This calculator does the reverse sum. It takes that tax-inclusive price and a GST rate, and separates the price into the taxable value and the GST portion.
Small business owners need this to record purchases correctly, because the taxable value and the tax go into different lines of the books and input tax credit is claimed only on the tax. Consumers use it out of curiosity or to check an expense claim. A café owner in Bengaluru buying supplies from a retail store, where only a total is printed, can use it to find the input GST she may be able to claim.
1. Note the inclusive price P and the GST rate R.
2. Divide P by (1 + R ÷ 100). Equivalently, taxable value = P × 100 ÷ (100 + R).
3. GST portion = P − taxable value.
4. As a shortcut, GST = P × R ÷ (100 + R).
5. If the sale was within one state, split the GST equally into CGST and SGST.
6. Check by adding R% to the taxable value to get P back.
An inclusive price is the base plus R% of the base, so P = base × (1 + R ÷ 100). To recover the base you divide both sides by (1 + R ÷ 100). Subtracting R% of P gives the wrong answer because R% was never calculated on P. The error is small at 5% but noticeable at 18% and large at 40%. On a ₹14,000 inclusive price at 40%, the correct base is ₹10,000, while subtracting 40% of 14,000 would wrongly give ₹8,400.
The GST share of an inclusive price is R ÷ (100 + R). At 5% this is 1 ÷ 21, about 4.76%. At 18% it is 18 ÷ 118, about 15.25%. At 40% it is 40 ÷ 140, about 28.57%. Remembering these three fractions makes quick mental checks easy. For example, a ₹1,050 item at 5% must carry ₹50 of GST, and a ₹590 item at 18% must carry ₹90.
Invoices are rounded to the paisa or the rupee, and some bills show GST computed line by line. So the figure you get by removing GST from a rounded total can differ from the bill by a few paise. That is normal. For accounting, use the taxable value and tax printed on a proper tax invoice if one is available, and use this calculation where only an inclusive total is shown.
Ayesha runs a café in Bengaluru and buys packaging material from a retail store for ₹2,625, a price that already includes 5% GST. She wants the taxable value for her purchase register.
Answer: Taxable value (before GST) ₹2,500; GST amount ₹125
Taking R% of the inclusive price as the tax.
Assuming every retail price includes GST. B2B quotes are usually exclusive.
Using the wrong slab for the item after the GST 2.0 changes.
Claiming input tax credit from a price tag alone when credit requires a proper tax invoice.
Recording purchases from retail receipts in the accounts.
Checking how much of a consumer price is tax.
Setting a base price so that the final price after GST is a target round number.
Reconciling expense claims that show only totals.
When would I need to remove GST from a price?
This is common when a price already includes GST, and you need to know the price before tax — for accounting, or to check an invoice is correct.