How the discount calculator works
A discount reduces the original price by a percentage or a fixed amount. This calculator answers the two most common shopping questions in one place:
- Percent off — enter the original price and the discount percentage to get the sale price and how much you save.
- Find discount % — enter the original price and the sale price to work out the discount percentage.
Example
A shirt costs $80 and is on sale for 25% off. 25% of 80 is 80 × 0.25 = 20, so you save $20 and pay $60.
A pair of shoes was $120 and is now $90. (120 − 90) ÷ 120 × 100 = 25% off.
Notes and assumptions
- All amounts use exact decimal arithmetic, so there are no floating-point surprises.
- A negative discount percentage means the sale price is higher than the original — the calculator shows the value instead of hiding it.
- The original price cannot be zero when finding the discount percentage, because dividing by zero is undefined.
Frequently asked questions
How do I calculate 20% off?
Multiply the original price by 0.20 to find the savings, then subtract from the original price. For $50: 50 × 0.20 = $10 off, so you pay $40.
How do I find the original price before a discount?
Divide the sale price by (1 − discount ÷ 100). A $60 price after 25% off came from 60 ÷ 0.75 = $80.
What is the difference between a discount and a markdown?
They are usually the same for shoppers: both lower the price from the original. In retail accounting, markdown specifically refers to a permanent price reduction.
Can a discount be more than 100%?
A discount over 100% would make the price negative, which does not happen in normal retail. The calculator accepts 0% to 100%.