Percentage Decrease Calculator
Calculate the percentage decrease between two values.
About Percentage Decrease Calculator
Percentage decrease measures how much a value has shrunk relative to its original value.
$$\% \text{ decrease} = \frac{\text{old} - \text{new}}{\text{old}} \times 100$$
How to use this calculator
- Enter the original, or old, value in the first box.
- Enter the smaller, new value in the second box.
- Click calculate to find the percentage decrease.
- Check the result to see how big the drop is relative to the original value.
The formula explained
The formula computes the size of the decrease as a fraction of the original value, then converts that fraction into a percent. It only works directly when the new value is less than the old value.
- old = the starting value before the decrease
- new = the smaller value after the decrease
- % decrease = how much the value decreased, written as a percentage
Step by step method
- Subtract the new value from the old value to find the amount of decrease.
- Divide that decrease by the old value to compare it to the starting amount.
- Multiply by 100 to change the decimal into a percentage.
Worked example
Problem. A jacket was priced at $80 and later sold for $60. Find the percentage decrease.
- Find the decrease: 80 - 60 = 20.
- Divide by the original value: 20 ÷ 80 = 0.25.
- Convert to a percent: 0.25 × 100 = 25%.
Answer. The percentage decrease is 25%.
Tips and common mistakes
- Make sure the old value is the larger, starting number, because the formula measures decrease from that amount.
- If the new value is greater than the old value, this is not a decrease, so you need a percentage increase instead.
Frequently asked questions
How do I use a percentage decrease calculator?+
Enter the original value as the old number and the smaller value as the new number. The calculator subtracts new from old, divides by old, and multiplies by 100 to give the percent decrease.
What does the formula for percentage decrease mean?+
The formula, (old - new) / old × 100, shows what fraction of the original value was lost. If the old value was 200 and the new value was 150, the decrease is 25% because 50 is one quarter of 200.
What if the new value is bigger than the old value?+
Then the result is not a percentage decrease, it is a percentage increase. In that case, the same calculator logic will produce a negative decrease or you should use a percentage increase calculator instead.
Can I use this for prices, scores, or measurements?+
Yes, as long as the two numbers use the same unit or scale. For example, you can compare dollars to dollars, points to points, or grams to grams.
How do I interpret a result like 12.5% decrease?+
It means the new value is 12.5% lower than the original value. So if something dropped from 80 to 70, that is a 12.5% decrease because the change is 10 out of 80.
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