Calculate the percentage decrease between two values or find the new value after decreasing a number by a percentage.
Enter both values to calculate the percentage decrease.
Enter a value and a percentage to see the decrease.
Percentage decrease measures how much a value has shrunk relative to where it started, expressed as a percentage. It answers a simple question: "how much smaller is the new number, relative to the original?" — rather than just showing the raw difference between the two.
The original value minus the new value gives the raw decrease amount. Dividing that by the original value expresses the decrease relative to where the value started. Multiplying by 100 converts that fraction into a percentage.
| Original Value | New Value | Decrease | Percentage Decrease |
|---|---|---|---|
| 100 | 80 | 20 | 20% |
| 200 | 150 | 50 | 25% |
| 50 | 25 | 25 | 50% |
| 1,000 | 800 | 200 | 20% |
| 500 | 425 | 75 | 15% |
These two ideas are easy to mix up, and mixing them up changes the story a number tells. Say a percentage changes from 30% to 20%:
Both descriptions are correct, but they answer different questions. "10 percentage points" describes the raw gap between the two percentages. "33.33% decrease" describes how large that gap is relative to the starting percentage. Going from 30% to 20% should never be casually called "a 10% decrease" without making clear which of these two numbers you mean.
"Percentage decrease" specifically describes a reduction from an original value to a smaller one. "Percentage change" is the broader, more general term — it can describe either an increase or a decrease, and is often written with a plus or minus sign to show which direction the value moved. If you already know a value went down and want to describe it plainly, "percentage decrease" is the more specific and useful term.
Percentage decrease comes up anywhere a value shrinks over time or between two states: price reductions, sales and discounts, expense reductions, business cost changes, population changes, performance measurements, budget reductions, and statistical comparisons.
A percentage decrease measures how much a value has shrunk relative to its original value, expressed as a percentage. Going from 100 to 75 is a 25% decrease.
Subtract the new value from the original value, divide the result by the original value, then multiply by 100: ((Original − New) ÷ Original) × 100.
Percentage Decrease = ((Original Value − New Value) ÷ Original Value) × 100.
Multiply the value by 0.10 to get the decrease amount, then subtract that from the original value. Or multiply the original value directly by 0.90. Either way, 100 decreased by 10% is 90.
Percentage points measure the raw gap between two percentages (30% to 20% is a 10 percentage-point decrease). Percentage decrease measures that same change relative to the starting percentage (((30 − 20) ÷ 30) × 100 = 33.33%). They answer different questions and shouldn't be used interchangeably.
If the new value is larger than the original value, the relative change is an increase, not a decrease — this calculator will tell you that plainly and show the percentage increase instead, rather than displaying a negative "decrease."
That represents a percentage increase. This calculator detects that automatically and labels the result as an increase with the correct percentage, instead of showing a misleading negative decrease.
Multiply the original value by the percentage and divide by 100 to get the decrease amount, then subtract that from the original value. Switch to the "Decrease a Value" mode above to do this instantly.
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