Plot No. 12 · Everyday & Shopping
Discount Calculator
Work out the sale price and how much you save when an item is marked down. Enter the original price and the discount percentage to see the new price instantly, and add a sales tax rate to find the final amount you will pay.
Sale price = original price minus (original price times discount percentage). The optional tax field is applied to the discounted price.
The link saves your inputs so you can bookmark or share this exact result.
How the discount is calculated
This calculator works out the sale price and the cash you save when an item is marked down. It multiplies the original price by the discount percentage to find the amount saved, then subtracts that from the original price to give the sale price. An optional sales tax field then applies tax to the discounted figure to show the final amount you would actually pay.
Crucially the tax is added after the discount, which matches how a till works: you are taxed on the reduced price, not the original. That ordering keeps the final figure honest.
How to use the discount calculator
- Enter the original price before the discount.
- Enter the discount percentage shown on the label or the deal.
- Optionally add a sales tax rate, then read the sale price, the amount saved and the final price after tax.
Worked examples
Twenty-five percent off an 80 item
Inputs: Original price 80, discount 25 percent, no tax.
Result: A saving of 20 and a sale price of 60.
Adding tax to the deal
Inputs: Original price 80, discount 25 percent, sales tax 8 percent.
Result: The sale price is still 60, but the final price after tax is about 64.80, since the 8 percent is applied to the discounted 60.
Limitations and common mistakes
Edge cases and limitations
- The discount is clamped between 0 and 100 percent, so you cannot enter a markup here.
- Tax is applied only to the discounted price, which is the usual order but may differ from regions that tax before discount.
- Figures are shown to two decimal places and do not handle multi-buy or buy-one-get-one offers, which need separate maths.
Common mistakes
- Stacking two discounts by adding the percentages. Two 20 percent discounts give 36 percent off in total, not 40, because the second applies to the already reduced price.
- Entering the sale price instead of the original price, which makes the saving look smaller than it is.
Frequently asked questions
How do I calculate a discount?
Multiply the original price by the discount percentage written as a decimal to find the amount saved, then subtract that from the original price. For example, 25 percent off 80 is 80 times 0.25, which is 20 saved, leaving a sale price of 60.
Does the calculator include sales tax or VAT?
It can. Leave the tax field at zero for a tax free figure, or enter your local rate to see the final price after tax is added on top of the discounted amount.
How do I stack two discounts?
Discounts usually apply one after another rather than adding together. Apply the first discount, then run the result through the calculator again with the second percentage. Two 20 percent discounts give 36 percent off in total, not 40 percent.
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