How to Calculate Percentage Decrease: Formula and Examples

Learning how to find percentage decrease is a useful skill for students, shoppers, and anyone who wants to understand changes in numbers. When a value gets smaller, such as prices dropping, scores going down, or quantities being reduced, knowing the percentage decrease helps us see by how much things changed.

Quick Start: Percentage Decrease Calculator

Before working through problems, you can use an online percentage decrease calculator. With this tool, simply enter the original number and the new number. It instantly gives you the percentage decrease, saving time and helping avoid mistakes. This is handy for checking your answers or doing quick calculations while shopping, studying, or budgeting.

What Is Percentage Decrease?

Percentage decrease tells you how much a number has gone down compared to where it started. For example, if the number of apples in a basket drops from 50 to 40, you may want to know by what percentage the apples decreased.

The formula is:

Percentage Decrease = (Original Value - New Value) / Original Value × 100

Step-by-Step Process

1. Find the difference

Subtract the new value from the original value to find how much it decreased.

2. Divide by the original value

This tells you what fraction of the original value was lost.

3. Multiply by 100

This changes the answer from a fraction to a percentage.

Example 1: Simple Purchase

A pen costs $10, and now it costs $7.

  • Difference = $10 - $7 = $3

  • Divide by original price: $3 ÷ $10 = 0.3

  • Multiply by 100: 0.3 × 100 = 30%

The pen’s price has decreased by 30%.

Example 2: School Scores

Last month, a student scored 80 on a quiz. This month, the score is 60.

  • Difference = 80 - 60 = 20

  • 20 ÷ 80 = 0.25

  • 0.25 × 100 = 25%

The score decreased by 25%.

Example 3: Real Product

A fruit seller used to sell a dozen bananas for $40. The seller lowers the price to $36.

  • Difference = $40 - $36 = $4

  • 4 ÷ 40 = 0.1

  • 0.1 × 100 = 10%

The percent decrease in price is 10%.

How to Find New Value When Percentage Decrease Is Known

If you know the percentage decrease and the original value, you can also find the new value.

Example: A jacket cost $100. It's reduced by 25%.

  • First, change the percent to a decimal: 25% = 0.25

  • Multiply: 0.25 × $100 = $25

  • Subtract: $100 - $25 = $75

The new price of the jacket is $75.

Practice Problem

Try for yourself:
A cell phone costs $250. Its price drops to $200. By what percentage did the price decrease?

Real-life Applications of Percentage Decrease

Percentage decrease is a tool we use in many everyday situations:

Shopping Sales

Stores announce discounts; knowing percentage decrease helps calculate true savings.

School and Exams

Track if grades or test scores have dropped, and by how much.

Sports

See how much a team’s performance or scores fell from last season to this one.

Environment

Measure how pollution or rainfall levels change over the years.

Finance

Understand investment losses, reduced costs, or budget cuts.

Final Tips

  • Remember to always use the original value in your calculations.

  • Percentage decrease can be checked quickly using online calculators for accuracy.

  • Practice with your own numbers from daily life to get better at it.

Understanding percentage decrease lets you measure reductions in a clear way and helps you make smarter decisions from shopping to school and beyond.

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