How to Calculate Percent Decrease (Step-by-Step + Examples)

Calculating Percent Decrease

To calculate percent decrease, subtract the new value from the original value, divide by the original value, and multiply by 100. This tells you how much a value has gone down as a percentage.

Percent decrease is a common math skill used in school, test prep, and real life. You’ll see it in discounts, sales prices, population drops, and changes in data. In this lesson, we’ll go step-by-step so you can learn exactly how to solve percent decrease problems with confidence.

Percent Decrease Formula

\large \text{Percent Decrease} = \frac{\text{Original Value} - \text{New Value}}{\text{Original Value}} \times 100

Here is what that means:

• Original Value = the starting amount
• New Value = the amount after it decreased
• Decrease = how much the value went down

Steps to Calculate Percent Decrease

1. Find the decrease. Subtract the new value from the original value.
2. Divide by the original value. This compares the decrease to where you started.
3. Multiply by 100. This changes the decimal into a percent.

If you follow these three steps carefully, you can solve percent decrease problems every time.

Example 1: Find the Percent Decrease from 80 to 60

\large 80 \rightarrow 60

Step 1: Find the decrease.

\large 80 - 60 = 20

Step 2: Divide by the original value.

\large \frac{20}{80} = 0.25

Step 3: Multiply by 100.

\large 0.25 \times 100 = 25\%

Final Answer

\large 25\%

Example 2: Discount Problem

A jacket originally costs \$120 and is now on sale for \$90 . What is the percent decrease?

Step 1: Find the decrease.

\large 120 - 90 = 30

Step 2: Divide by the original value.

\large \frac{30}{120} = 0.25

Step 3: Multiply by 100.

\large 0.25 \times 100 = 25\%

Final Answer

\large 25\%

Example 3: Percent Decrease in a Number

A value decreases from 150 to 120 . What is the percent decrease?

Step 1: Find the decrease.

\large 150 - 120 = 30

Step 2: Divide by the original value.

\large \frac{30}{150} = 0.2

Step 3: Multiply by 100.

\large 0.2 \times 100 = 20\%

Final Answer

\large 20\%

Practice Problems: Calculate Percent Decrease

Try these on your own first, then check the answers below.

Practice Problems

Find the percent decrease for each problem.

1. A price drops from \$50 to \$40 .
2. A value decreases from 200 to 150 .
3. A number goes from 90 to 72 .
4. A video game originally costs \$60 and is marked down to \$45 .
5. A population decreases from 500 to 425 .

Watch Step-by-Step Example

Watch John explain how to solve percent decrease problems step-by-step:

Practice Problem Answers

1.  \Large \frac{50 - 40}{50} \times 100 = \frac{10}{50} \times 100 = 20\%

2.  \Large \frac{200 - 150}{200} \times 100 = \frac{50}{200} \times 100 = 25\%

3.  \Large \frac{90 - 72}{90} \times 100 = \frac{18}{90} \times 100 = 20\%

4.  \Large \frac{60 - 45}{60} \times 100 = \frac{15}{60} \times 100 = 25\%

5. \Large \frac{500 - 425}{500} \times 100 = \frac{75}{500} \times 100 = 15\%

Common Mistakes When Calculating Percent Decrease

• Dividing by the new value instead of the original value
  Always divide by the original value because percent decrease compares the drop to where the value started.
• Forgetting to multiply by 100
  If you stop at a decimal, your answer is not yet written as a percent.
• Subtracting in the wrong order
  Be careful to subtract new value from original value, not the other way around.
• Confusing percent decrease with percent increase
  Percent decrease is only used when the value goes down.

This is a very common place where students make mistakes, so take your time and follow the formula carefully.

Related Percent Tutorials

• • How to Find Percent of a Number
  • How to Calculate Percent Increase

Need More Help with Percents?

If you want more help with percent problems and other essential math skills, check out John’s full courses. They include clear instruction, practice problems, and step-by-step solution videos.

👉 Explore the Foundations Math Course
👉 Explore the Pre-Algebra Course

You can master this. Stay consistent, practice the steps, and keep going.