Discount calculator

How to use this page

1. Replace the sample numbers with your own. Nothing is sent to a server.
2. Read the result. It changes as you type.
3. Open the formula if you want to recompute the result by hand.
4. Copy the result if you want to keep it. The numbers you type stay in this browser and are not added to the address.

Formula

Sale price = price × (1 − first ÷ 100) × (1 − second ÷ 100). Tax = sale price × tax rate ÷ 100. Final = sale price + tax. Saved = original price − sale price, before tax. A check: 100 with 20% off and then 10% off is 72, not 70.

Sequence matters

Twenty percent off and then ten percent off leaves 72% of the price. Ten percent off and then twenty percent off also leaves 72%, because multiplication commutes. Adding the percents does not. Thirty percent off would leave 70. Stores sometimes advertise the added number. The register usually multiplies.

Tax is applied after the discounts, which is how a sales tax or VAT on a discounted shelf price usually works. If a tax was already inside the sticker, use the sales-tax page in extract mode before you discount, or you will tax the tax.

What saved means

Amount saved compares the original price with the sale price and ignores tax. You did not save the tax. You simply never spent the markdown. If you need the cash that leaves your account, read the final price.

A 100% first discount zeros the sale. A second discount then has nothing left to cut. That is arithmetic, not a coupon policy. Some stores exclude sale items from a second coupon. The page cannot know the shelf rule.

Easy mistakes

• Adding 20 and 10 to make a 30% discount.
• Putting tax into the price and also into the tax field.
• Comparing a sale without checking a fees line that the percent does not touch, such as shipping.