Percent decrease measures how much a value has declined relative to its original amount. It's frequently used to calculate discounts, price reductions, weight loss, and declining sales figures. By expressing the decrease as a percentage, you can compare reductions across different scales and understand the proportional impact of changes.
How to calculate percent decrease:
This formula calculates the percentage by which the original value has declined. The result is always positive when expressing a decrease.
For detailed step-by-step solutions and worked examples, explore our percentage change examples guide which walks through decreases, increases, negative values, and more.
Percent decrease calculations become problematic when the original value is zero or when working with negative numbers. When the original value equals zero, the formula is mathematically undefined because division by zero is impossible—there's no meaningful baseline from which to measure the percentage change. Negative values present a different challenge: if both the original and new values are negative, the calculation produces results that may not align with intuitive understanding of "decrease." Similarly, if the original value is negative and the new value is positive, or vice versa, percentage decrease loses practical meaning. In these situations, consider using absolute values, measuring change in absolute terms rather than percentages, or using our percentage change calculator which handles directional changes more naturally. For most real-world applications like pricing, inventory, and finance, you'll work with positive values where percent decrease operates as intended.
Use percent decrease when tracking reductions in sales, calculating discount percentages, measuring weight loss progress, analyzing declining test scores, or comparing before-and-after values where the result is lower. Percent decrease is particularly useful in retail for pricing strategies, in finance for measuring losses, and in health tracking for monitoring reductions over time. Unlike percent increase, percent decrease always starts from a higher original value.
Calculate percent decrease instantly with our percent change calculator. Simply enter your original and new values to get accurate results without manual calculations.
Percent decrease and discount are the same calculation. When a store offers a 20% discount, that's a 20% decrease from the original price. Both measure the reduction as a percentage of the original amount.
If you get a negative result when calculating percent decrease, it means the value actually increased rather than decreased. In this case, you should use percent increase instead to properly represent the change.
To reverse a percent decrease, you cannot simply add the same percentage back. For example, if something decreases by 20% and you want to restore it, you need to increase by 25%, not 20%. Use the formula: Original Value = New Value ÷ (1 - Decrease%/100)
The maximum percent decrease is 100%, which occurs when a value drops to zero. You cannot have a percent decrease greater than 100% because that would mean the new value is negative, which is impossible for most real-world measurements.