Percentage Decrease Calculator Guide
A percentage decrease measures how much a value has fallen, expressed as a percentage of the original value. If a price drops from $200 to $150, that is a 25% decrease — because the $50 drop is 25% of the original $200.
The formula is nearly identical to percentage increase, except you subtract the new value from the old. Getting this right matters for calculating discounts, evaluating investment losses, tracking statistical changes, and comparing any two values over time.
The Formula
Percentage Decrease = ((Old Value − New Value) / Old Value) × 100 Examples: Price drops from $200 to $150: ((200 − 150) / 200) × 100 = (50/200) × 100 = 25% decrease Stock falls from $85 to $68: ((85 − 68) / 85) × 100 = (17/85) × 100 = 20% decrease Weight loss: 180 lb to 162 lb: ((180 − 162) / 180) × 100 = (18/180) × 100 = 10% decrease
Calculating Discounts
Retail discounts are percentage decreases. A '30% off' sale on a $120 item: 30% of $120 = $36, so the sale price is $120 − $36 = $84. Alternatively: $120 × (1 − 0.30) = $120 × 0.70 = $84. The second method is faster for mental math.
To find the original price from a discounted price: divide the sale price by (1 − discount rate). If a $84 price is 30% off: $84 ÷ 0.70 = $120 original price.
Percentage Decrease Is Not Symmetric with Increase
A 50% increase followed by a 50% decrease does not return you to the original value. If $100 increases by 50%: $150. Then decreases by 50%: $75. You end up lower. This is because the percentage decrease is applied to the larger value.
Similarly, recovering a 50% loss requires a 100% gain: $100 → $50 (−50%) → $100 (×100% gain). This asymmetry is crucial in investing — avoiding large losses matters more than capturing large gains.
Quick Tips
- ✓
Discount shortcut: multiply price by (1 − discount). 25% off $80: 80 × 0.75 = $60.
- ✓
Find the original price: divide sale price by (1 − discount rate). $60 at 25% off: 60 ÷ 0.75 = $80.
- ✓
A 10% decrease leaves 90% of the original. A 20% decrease leaves 80%. Subtract the percentage from 100% to find the remaining fraction.
- ✓
Investment losses: a 50% loss needs a 100% gain to recover. A 25% loss needs a 33% gain to recover.
Frequently Asked Questions
What is a 20% decrease of 500?
20% of 500 = 100. 500 − 100 = 400. Or: 500 × 0.80 = 400.
If a stock drops 40%, how much gain is needed to recover?
Let the original be 100. After −40%, it is 60. To get back to 100 from 60: (100 − 60)/60 = 40/60 = 66.7% gain needed.
What is 15% off $79.99?
$79.99 × 0.85 = $67.99. (Or: $79.99 × 0.15 = $12.00 discount; $79.99 − $12.00 = $67.99.)
Can a percentage decrease exceed 100%?
No — a 100% decrease reduces a value to zero. A value cannot decrease more than 100% of itself (it cannot go below zero in most real-world contexts). Values that cross zero into negative territory require different framing.
Related Tools
Related Guides
Percentage Increase Calculator Guide
5 min read
Percentage Calculator Guide
5 min read
How to Calculate Tips
5 min read
Unit Price Calculator Guide
4 min read
Finance Calculator Guide: Every Financial Tool on Apex Conversion
10 min read
📏 LengthWhat Is a Kilometer? Definition, Uses, and Conversion Guide
5 min read
Sources
All conversion results are provided for general informational purposes only. Read our full disclaimer.