How to Find Percent of Increase and Decrease? (+FREE Worksheet!)
The percent of increase and decrease measures how much a quantity has changed relative to its original value. Whether you are comparing prices, populations, test scores, or temperatures, this single formula handles both increases and decreases. This lesson breaks the concept down step by step with clear examples and practice problems.
What Is Percent of Increase and Decrease?
Percent of change (also called percent of increase or decrease) tells you what fraction of the original value the change represents, expressed as a percentage.
Percent Change = ((New Value – Original Value) ÷ Original Value) × 100
- If the result is positive, there was an increase.
- If the result is negative, there was a decrease.
How to Calculate Percent of Increase and Decrease
Percent of Increase
Used when the new value is greater than the original.
- From 40 to 50: (50 – 40) ÷ 40 × 100 = 10/40 × 100 = 25\% increase.
- From 25 to 35: (35 – 25) ÷ 25 × 100 = 10/25 × 100 = 40\% increase.
Percent of Decrease
Used when the new value is less than the original. Take the absolute value of the result and label it a decrease.
- From 80 to 60: |60 – 80| ÷ 80 × 100 = 20/80 × 100 = 25\% decrease.
- From 120 to 90: |90 – 120| ÷ 120 × 100 = 30/120 × 100 = 25\% decrease.
Step-by-Step Summary
- Identify the original value (starting amount) and the new value (ending amount).
- Subtract: New – Original. (Negative means decrease.)
- Divide the result by the original value.
- Multiply by 100 to convert to a percent.
- Label the answer as an increase or decrease.
Watch: Percent of Change — Increase and Decrease
Math with Mr. J explains both percent increase and decrease with clear, worked examples:
Percent of Increase and Decrease – Worked Examples
Example 1: A shirt originally cost $40. The new price is $50. What is the percent of increase?
(50 – 40) ÷ 40 × 100 = 10 ÷ 40 × 100 = 25\% increase.
Example 2: A population dropped from 80,000 to 60,000. What is the percent of decrease?
(80,000 – 60,000) ÷ 80,000 × 100 = 20,000 ÷ 80,000 × 100 = 25\% decrease.
Example 3: A student’s score went from 25 to 35. What is the percent of increase?
(35 – 25) ÷ 25 × 100 = 10 ÷ 25 × 100 = 40\% increase.
Example 4: A car’s value fell from $120 to $90. What is the percent of decrease?
(120 – 90) ÷ 120 × 100 = 30 ÷ 120 × 100 = 25\% decrease.
More Practice: Percent Change Step-by-Step
Math with Mr. J provides an additional step-by-step guide to percent change with more examples:
Exercises for Percent of Increase and Decrease
Find the percent of change for each pair of values.
- From 50 to 75
- From 200 to 150
- From 30 to 45
- From 60 to 48
- From 10 to 13
- From 500 to 425
Answers
- 50\% increase
- 25\% decrease
- 50\% increase
- 20\% decrease
- 30\% increase
- 15\% decrease
Want More Practice?
We haven’t published a worksheet built specifically for Percent of Increase and Decrease just yet. In the meantime, the free worksheets below cover closely related skills and concepts. If you’d like extra practice, download any that look helpful, complete the problems, and check your work — they’re a great way to reinforce what you learned on this page and strengthen the foundations this topic builds on:
Frequently Asked Questions
What is the formula for percent of change?
Percent Change = ((New Value – Original Value) ÷ Original Value) × 100. A positive result is an increase; a negative result is a decrease.
Do I always divide by the original value?
Yes. The original (starting) value is always in the denominator. Dividing by the new value gives a different — and incorrect — answer.
How is percent of change different from the actual change?
The actual change is just the difference (New – Original). The percent of change expresses that difference as a fraction of the original, which puts changes of different sizes on a common scale.
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