Percentage Decrease Calculator
This percentage decrease calculator finds the percent drop between two values, the value after a decrease, or the original value. Example: a value falling from 80 to 60 has decreased by 25 %.
Example: What do you want to find: Percent decrease · Original value 80 · New value 60 → Result: Decrease of 25 % (from 80 to 60). Source: Wikipedia – Prozentrechnung. Updated: .
How it is calculated
The percentage decrease shows what share of the starting value has been lost. It always refers to the old value, not the new one – the most common source of mistakes.
Formulas
The percent decrease is (old − new) / old · 100. To find the new value after a known decrease, multiply the old value by (1 − p/100). To go back to the original, divide the new value by (1 − p/100). The calculator shows the difference, the factor and each step.
Three examples
From 80 to 60: the difference is 20, so 20 / 80 = 25 %. A price of 200 drops 15 %: 200 · 0.85 = 170. If something costs 170 after a 15 % discount, it was 170 / 0.85 = 200 before. If a price rose from 60 to 80, that would not be a decrease but an increase of 33.33 %.
- A factor of 0.75 corresponds to a 25 % decrease.
- Two decreases of 10 % each add up to 19 %, not 20 %, because the second one acts on the smaller value.
Frequently asked questions
How do you calculate percentage decrease?
Subtract the new value from the old, divide by the old value and multiply by 100. From 80 to 60 that gives 25 %.
Why does a 25 % increase not cancel a 25 % decrease?
Because the two percentages act on different bases. After −25 %, 100 becomes 75; to get back to 100 you need +33.33 %.
How do I work back to the original value?
Divide the new value by (1 − percentage/100). For 170 after a 15 % decrease that is 170 / 0.85 = 200.
Sources and legal basis
As of: · Editorial policy
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