Percentage Decrease Calculator
Find the percentage drop between two values.
Calculation mode
Starting value before the change.
Value after the change. If it is higher, the result is an increase.
Percentage decrease
20%
Percent drop relative to the original value.
New / final value
80
Value after the decrease.
Original value
100
Decrease amount
20
Remaining percentage
80%
Mode
Original value to new value
Formula used
Percentage Decrease = (Original Value − New Value) ÷ Original Value × 100
(100 − 80) ÷ 100 × 100
Percentage Decrease Formulas
Decrease Amount
Decrease Amount = Original Value − New Value
Percentage Decrease
Percentage Decrease = (Original Value − New Value) ÷ Original Value × 100
New Value After Decrease
New Value = Original Value × (1 − Percentage Decrease ÷ 100)
Reverse Original Value
Original Value = New Value ÷ (1 − Percentage Decrease ÷ 100)
Remaining Percentage
Remaining Percentage = 100% − Percentage Decrease
Variable Explanations
Original value
Starting value, and the base (denominator) of every percentage decrease.
New value
Value after the change. If it is higher than the original, the change is an increase.
Decrease amount
Original value minus new value: the absolute drop.
Percentage decrease
Decrease amount as a percent of the original value. It is a relative change, not percentage points.
Remaining percentage
New value as a percent of the original. A 25% decrease leaves 75%.
Calculated original value
In reverse modes, the exact starting value worked out from the final value or decrease amount.
Worked Examples
Decrease from 100 to 80
Formula: (100 − 80) ÷ 100 × 100
Answer: 20%
The value dropped by 20, which is 20% of 100.
Decrease from 250 to 200
Formula: (250 − 200) ÷ 250 × 100
Answer: 20%
The decrease amount is 50.
Price after 25% decrease from 80
Formula: 80 × (1 − 25 ÷ 100)
Answer: 60
A 25% decrease means 75% remains.
Original from final 60 after 25% decrease
Formula: 60 ÷ 0.75
Answer: 80
Reverse decrease divides by the remaining percentage.
Remaining percentage after a 65% decrease
Formula: 100% − 65% = 35% remaining
Answer: 35% remains
Remaining percentage is 100% minus the percentage decrease.
New value higher than original
Formula: (120 − 100) ÷ 100 × 100
Answer: 20% increase
This is not a decrease, so the increase formula applies.
20% decrease then 20% increase
Formula: 100 → 80 → 96
Answer: Not back to 100
The second percent uses a different base.
Decimal value example
Formula: (12.5 − 10) ÷ 12.5 × 100
Answer: 20%
Decimals work the same way.
Percentage Decrease vs Percentage Change
Percentage decrease
Percentage decrease is a positive percent drop when the new value is lower than the original. Example: 100 to 80 is a 20% decrease.
Percentage change
Percentage change can be positive or negative. Example: 80 to 100 is a 25% increase because the base is now 80.
Reverse Percentage Decrease
Reverse percentage decrease finds the original value before a decrease. Do not simply add the percentage back to the final value. If 60 is the value after a 25% decrease, then 60 is 75% of the original. Original value = 60 ÷ 0.75 = 80.
Common Percentage Decrease Mistakes
Frequently Asked Questions
Subtract the new value from the original value, divide by the original value, then multiply by 100.
Percentage Decrease = (Original Value − New Value) ÷ Original Value × 100.
Decrease amount is the absolute drop. Percentage decrease shows that drop as a percent of the original value.
Percentage decrease compares the drop to the starting value, so the original value is the base.
Use New Value = Original Value × (1 − Percentage Decrease ÷ 100).
Divide the final value by the remaining percentage. For example, after a 25% decrease, divide by 0.75.
For ordinary positive values, a decrease greater than 100% usually means the final value went below zero or the inputs need review.
Then it is a percentage increase, not a percentage decrease.
The increase is applied to the smaller value after the decrease, so the base changes.
No. Percentage decrease is relative change. Percentage points describe the absolute difference between two percentages.
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