Find out what you actually pay after a discount, and how much you save. If GST applies, it is worked out on the discounted price.
The discount is calculated on the original price and subtracted from it.
If GST applies, it is charged on the discounted price, not the original — this is how invoices are raised under GST.
The saving is shown both as an amount and as a percentage.
Discount: Price × Discount% ÷ 100
Price after discount: Price − Discount
Final price: Discounted price + GST on that price
The discount calculator tells you what you will actually pay after a percentage discount, how much you save, and, if GST applies, what the final bill is once tax is added on the discounted price. It is built for the way Indian invoices work: the discount is deducted first and GST is charged on the reduced value, so a bigger discount lowers the tax as well.
Shoppers use it during festive sales and online sale events to check what '20% off' really means. Shopkeepers and small businesses use it when quoting prices, and students meet the same calculation in class 8 maths. Seeing the discount, the price after discount, the GST and the final price as separate lines makes it easier to compare offers across stores and platforms.
1. Note the original price before discount.
2. Discount amount = Price × Discount% ÷ 100.
3. Price after discount = Price − Discount amount.
4. If GST applies after discount, GST = Price after discount × GST% ÷ 100.
5. Final price = Price after discount + GST.
6. Saving % = Discount amount ÷ Original price × 100.
Under GST, tax is charged on the transaction value. A discount shown on the invoice at the time of sale reduces that value, so GST is computed on the discounted price. The result is Final = P × (1 − d) × (1 + g), where d is the discount rate and g the GST rate. Because the two factors multiply, the order does not change the final number mathematically, but the invoice must show the discount first and tax on the lower value.
Two discounts of 20% each do not make 40%. The first leaves 0.8 of the price, and the second is taken on that reduced price, leaving 0.8 × 0.8 = 0.64. The effective discount is 36%. In general, successive discounts d₁ and d₂ give an effective discount of 1 − (1 − d₁)(1 − d₂). The same logic applies to 'extra 10% off on sale price' offers, and it is why a flat 40% off is always better than 20% plus 20%.
In retail, the MRP already includes GST, so a discount on MRP gives the final price directly and no GST is added. This calculator's GST option is for prices quoted before tax, as in business quotations and many B2B catalogues. If you are buying from a shop at MRP, leave GST at 0. If a quotation says 'plus GST', select the rate so the calculator adds tax on the discounted amount.
Aarti is buying a mixer grinder for her Chennai home from a dealer who quotes ₹6,800 before tax. He offers 15% off during the festive sale and adds GST at 18% on the discounted price.
Answer: Final price ₹6,820; You save ₹1,020; Price after discount ₹5,780
Adding GST to an MRP that already includes it.
Adding two successive discount percentages instead of multiplying the remaining fractions.
Calculating GST on the original price instead of the discounted price.
Confusing 'save ₹X' with the percentage saved on the original price.
Checking real prices during festive and online sales.
Preparing quotations with discount and GST for customers.
Comparing a percentage discount with a flat cashback offer.
Solving profit, loss and discount problems in school maths.
Is GST charged before or after the discount?
After. When a discount is shown on the invoice at the time of sale, GST is charged on the lower price. So a bigger discount lowers both the price and the tax.
How do I calculate two successive discounts?
Apply them one after the other, not by adding them together. Two 20% discounts in a row are not 40% off — they leave 0.8 × 0.8 = 0.64 of the price, which is actually 36% off.