Percentage decrease shows how much a number has gone down compared with its original value. It is useful for price drops, cost reductions, lower sales, reduced traffic, weight loss, fewer errors, and any situation where a value falls from one number to another.
Use the calculator to check the number quickly, then read the guide for formulas, examples, and common mistakes.
What Is Percentage Decrease?
Percentage decrease measures how much a value has fallen from its original amount.
For example, if a price drops from 100 to 80, the decrease amount is 20.
Compared with the original value of 100, that decrease is 20%.
Percentage Decrease Formula
The percentage decrease formula is: percentage decrease = decrease amount ÷ original value × 100.
The decrease amount is the original value minus the new value.
The full formula is: percentage decrease = (original value - new value) ÷ original value × 100.
Step 1: Find the Original Value
The original value is the number before the decrease happened.
This is the base of the calculation.
If a price falls from 250 to 200, the original value is 250.
Step 2: Find the New Value
The new value is the number after the decrease happened.
In the same example, the new value is 200.
The decrease is measured by comparing 200 with the original value of 250.
Step 3: Calculate the Decrease Amount
Subtract the new value from the original value.
250 - 200 = 50.
The decrease amount is 50.
Step 4: Divide by the Original Value
Now divide the decrease amount by the original value.
50 ÷ 250 = 0.20.
This shows the decrease as a decimal.
Step 5: Multiply by 100
Multiply the decimal by 100 to convert it into a percentage.
0.20 × 100 = 20%.
So the value decreased by 20%.
Example: Price Decrease
Suppose a product price drops from 120 to 90.
The decrease amount is 120 - 90 = 30.
Percentage decrease is 30 ÷ 120 × 100, which equals 25%.
Example: Cost Decrease
Suppose a monthly cost falls from 500 to 425.
The decrease amount is 75.
Percentage decrease is 75 ÷ 500 × 100, which equals 15%.
Example: Traffic Decrease
Suppose visits fall from 10,000 to 8,000.
The decrease amount is 2,000.
Percentage decrease is 2,000 ÷ 10,000 × 100, which equals 20%.
Percentage Decrease vs Percentage Change
Percentage decrease is one type of percentage change. It is used when the new value is lower than the original value.
Percentage change can describe both increase and decrease.
For the general before-and-after calculation, read Percentage Change Formula.
Percentage Decrease and Discounts
Discounts are a common form of percentage decrease because the price goes down from the original price.
For example, 20% off means the price is reduced by 20% of the original price.
For discount-specific examples, use the Discount Calculator or read Discount Formula.
Common Mistakes to Avoid
The first mistake is dividing by the new lower value instead of the original value.
The second mistake is forgetting that the decrease is measured from the starting number.
The third mistake is assuming a percentage decrease and the same percentage increase cancel each other out. For example, a 20% decrease followed by a 20% increase does not return to the original value.
Use the Calculator
Use the Percentage Calculator to check percentage values quickly.
For the main percentage guide, read How to Calculate Percentage.
For percentage increase, read Percentage Increase Formula.
Conclusion
To calculate percentage decrease, subtract the new value from the original value, divide by the original value, and multiply by 100.
The original value is the key base number because the decrease is measured from where the value started.
Related guides and tools
FAQs
What is the percentage decrease formula?
Percentage decrease = (original value - new value) divided by original value, multiplied by 100.
What is the percentage decrease from 120 to 90?
The decrease is 30, and 30 divided by 120 multiplied by 100 equals 25%.
Is a discount a percentage decrease?
Yes, a percentage discount is a decrease from the original price.
Should I divide by the old value or new value?
Use the old value because percentage decrease is measured from the starting number.