What's the difference between percentage change and percentage of a number?

Percentage of a number answers questions like “What is 20% of 80?”, while percentage change compares the difference between two values relative to the original amount. Use the change tab whenever you are moving from a starting value to a new value.

How do I convert between decimals, fractions, and percentages?

Multiply a decimal by 100 to get a percentage (e.g., 0.375 → 37.5%). Divide a percentage by 100 to get a decimal, or place it over 100 and simplify to get a fraction.

Why does the percentage change depend on the starting value?

Percentage change measures growth relative to the original amount. A $10 increase on $20 is 50%, but the same $10 increase on $200 is only 5%, because the base amount is larger.

Can a percentage be greater than 100%?

Yes. Percentages over 100% mean the part is larger than the whole. For example, earning 150% of a target means you achieved one and a half times the goal.

Percentage Calculator

Calculate percentages and percentage changes

Method and source check

Last checked: Sep 17, 2026

Editorial check of method and sources; this is not professional review or advice.

Method

The calculator supports percentage of a number, percentage change from an original value, and finding what percentage one value is of another.

part = (percentage / 100) × whole

percentage change = ((new − original) / original) × 100

percentage = (part / whole) × 100

Variables and units

part: the amount being compared
whole: the reference amount
original / new: starting / ending values

Worked example

A change from 50 to 60 is ((60 − 50) / 50) × 100 = 20%.

Limitations

The numeric result is rounded to at most two decimal places, with no trailing zero padding. The explanatory formula and sentence interpolate the unrounded intermediate value.

The reference denominator must not be zero. Results are general arithmetic and do not include domain-specific tax, financial, medical, or statistical rules.
Percentage-of input 25% and 80 returns 20.
Percentage-change input original 50 and new 60 returns 20%; an original value of 0 fails validation.
Find-percentage input part 1 and whole 3 returns a numeric result of 33.33%, while the formula text uses the unrounded 33.33333333333333%; a whole value of 0 fails validation.

Sources

Solve General Applications of Percent — OpenStax, Rice University(opens in a new tab)

Table of Contents

How to Use

Select the type of percentage calculation
Enter the required values
Click calculate to see the result
View step-by-step explanation

What are Percentages?

A percentage is a way of expressing a number as a fraction of 100. The word "percent" comes from the Latin "per centum," meaning "by the hundred." Percentages are used to describe proportions, changes, and relationships between numbers in a standardized way.

Key Formula

Percentage = (Part ÷ Whole) × 100

Types of Percentage Calculations

1. Percentage of a Number

Question: What is X% of Y?

Formula: (X ÷ 100) × Y

Example: What is 25% of 80? = (25 ÷ 100) × 80 = 20

2. Percentage Change

Question: What is the percentage change from X to Y?

Formula: ((New Value - Original Value) ÷ Original Value) × 100

Example: Change from 50 to 60 = ((60 - 50) ÷ 50) × 100 = 20%

3. Find the Percentage

Question: X is what percentage of Y?

Formula: (X ÷ Y) × 100

Example: 15 is what % of 60? = (15 ÷ 60) × 100 = 25%

Real-World Applications

Percentages are used extensively in everyday life and business:

Financial Applications

Interest rates and loan calculations
Tax calculations
Investment returns
Discounts and sales
Commission calculations

Business & Analytics

Market share analysis
Performance metrics
Growth rates
Profit margins
Statistical analysis

Daily Life

Tips and gratuities
Battery levels
Grades and test scores
Weather probability
Recipe scaling

Science & Medicine

Concentration levels
Success rates
Error margins
Efficiency calculations
Dosage calculations

Percentage Tips & Tricks

Quick Mental Math

10%: Move decimal point one place left (10% of 250 = 25)
1%: Move decimal point two places left (1% of 250 = 2.5)
50%: Divide by 2 (50% of 80 = 40)
25%: Divide by 4 (25% of 80 = 20)
20%: Divide by 5 (20% of 100 = 20)

Common Mistakes to Avoid

Don't forget to multiply by 100 when converting decimals to percentages
Be careful with percentage point vs percentage change
Remember: X% of Y = Y% of X (commutative property)
When calculating percentage change, use the original value as the denominator

Converting Between Forms

Decimal to Percentage: Multiply by 100 (0.25 = 25%)

Percentage to Decimal: Divide by 100 (25% = 0.25)

Fraction to Percentage: Divide and multiply by 100 (1/4 = 0.25 = 25%)

Frequently Asked Questions

What's the difference between percentage change and percentage of a number?: Percentage of a number answers questions like “What is 20% of 80?”, while percentage change compares the difference between two values relative to the original amount. Use the change tab whenever you are moving from a starting value to a new value.
How do I convert between decimals, fractions, and percentages?: Multiply a decimal by 100 to get a percentage (e.g., 0.375 → 37.5%). Divide a percentage by 100 to get a decimal, or place it over 100 and simplify to get a fraction.
Why does the percentage change depend on the starting value?: Percentage change measures growth relative to the original amount. A $10 increase on $20 is 50%, but the same $10 increase on $200 is only 5%, because the base amount is larger.
Can a percentage be greater than 100%?: Yes. Percentages over 100% mean the part is larger than the whole. For example, earning 150% of a target means you achieved one and a half times the goal.

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