Percentage Decrease Calculator
Find the percentage decrease between two numbers, or cut a percentage from a number. Both update as you type.
Percentage decrease from one value to another
Amount removed
20
New value as a share of old
75%
Percentage decrease
−25%
(80 − 60) ÷ 80 × 100
Decrease a number by a percent
You know the percentage and want the new value.
Decrease X by P%
Amount removed
30
New value
170
200 × 0.85
The percentage decrease formula
Percentage decrease = (Old − New) ÷ Old × 100
You divide by the old value, because the fall is measured against where you started.
Worked example — 80 falls to 60
80 − 60 = 20
20 ÷ 80 = 0.25
0.25 × 100 = 25
So 80 to 60 is a 25% decrease.
Cutting a percentage from a number
New value = Old value × (1 − Percent ÷ 100)
Cutting 15% from 200 is 200 × 0.85 = 170. One multiplication beats working out 15% and subtracting it.
A decrease cannot exceed 100%
A fall of 100% takes a value to zero. Nothing positive can fall further while staying positive, so a "120% decrease" either means the value went negative or the figure is wrong. Increases have no such ceiling.
Up then down does not return you home
Add 10% to 100 and you get 110. Take 10% off 110 and you remove 11, not 10, leaving 99. The second percentage applied to a bigger base.
To undo a decrease of d percent you need an increase of d ÷ (100 − d) × 100 percent. Undoing a 50% fall takes a 100% rise. Undoing an 80% fall takes a 400% rise.
Common questions
- What is the percentage decrease formula?
- Percentage decrease = (old value − new value) ÷ old value × 100. Subtract the new value from the old one, divide by the old value, then multiply by 100.
- How do I decrease a number by a percentage?
- Multiply by 1 minus the percentage as a decimal. To cut 15% from 200: 200 × 0.85 = 170.
- Can a percentage decrease be more than 100%?
- Only if the value goes negative. A fall of exactly 100% takes the value to zero, and nothing can fall further than that while staying positive.
- Why does an increase then an equal decrease not return the original?
- The two percentages apply to different bases. Adding 10% to 100 gives 110, and taking 10% off 110 removes 11, leaving 99.