Percentage Calculator

Calculate percentages and percentage changes

Method and source check

Last checked: Jul 31, 2026

Source and implementation check; 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 reference denominator must not be zero. Results are general arithmetic and do not include domain-specific tax, financial, medical, or statistical rules.

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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