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Percentage Calculator | Find %, Change & Difference

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Last Update on April 4, 2026
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Free percentage calculator to find %, percentage change, increase/decrease & difference. Includes formulas, examples & step-by-step solutions.
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Percentage Calculator – Find Percentages, Percentage Change & Formulas Online

Free percentage finder for any type of percentage problem — instant results with formulas and step-by-step solutions

What is X% of Y? — Find a percentage of any number.

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X is what percent of Y? — Find the percentage one number is of another.

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X is P% of what number? — Reverse percentage finder.

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Increase or decrease a number by a percentage.

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How much has a value changed, as a percentage of the original?

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Percentage difference between two values — treats both values equally, no defined starting point.

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Quick Percentage Answers

Click any question to see the answer using standard percentage formulas.

What is 25% of 80?
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45 is what % of 60?
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30 is 15% of what?
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500 increased by 10%
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220 decreased by 12%
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% change from 80 to 100
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What is 15% of 200?
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% difference: 70 and 85
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Percentage Formula Cheat Sheet

Every percentage problem uses one of these five formulas. Bookmark this section as a quick reference.

What is X% of Y?
Result = (X ÷ 100) × Y

Multiply the whole by the decimal form of the percentage. Example: 20% of 150 = 0.20 × 150 = 30.

X is what % of Y?
% = (X ÷ Y) × 100

Divide the part by the whole, then scale to 100. Example: 45 ÷ 180 × 100 = 25%.

Reverse percentage
Whole = X ÷ (P ÷ 100)

Divide the known part by the decimal percentage. Example: 30 is 15% of what? 30 ÷ 0.15 = 200.

Percentage change
% change = ((New − Old) ÷ |Old|) × 100

Measures how much a value changed relative to where it started. Positive = increase; negative = decrease.

Percentage difference
% diff = |A − B| ÷ ((A+B) ÷ 2) × 100

Compares two values symmetrically — neither is the defined "original". Used when there's no natural starting point.

Increase / decrease by %
New = Original × (1 ± P ÷ 100)

Use + for increase, − for decrease. Example: 400 increased by 15% = 400 × 1.15 = 460.

Worked Examples

Example 1 – What is 15% of 200?

Given: 15% of 200
(15 ÷ 100) × 200
Step 1: Convert 15% to decimal → 0.15
Step 2: Multiply by 200 → 0.15 × 200
= 30

Example 2 – 45 is what percent of 60?

Part = 45, Whole = 60
(45 ÷ 60) × 100
Step 1: 45 ÷ 60 = 0.75
Step 2: 0.75 × 100 = 75
= 75%

Example 3 – 30 is 20% of what?

Part = 30, Percentage = 20%
30 ÷ (20 ÷ 100) = 30 ÷ 0.20
Step 1: Convert 20% to decimal → 0.20
Step 2: Divide 30 by 0.20
= 150

Example 4 – Increase 500 by 10%

Original = 500, Increase = 10%
500 × (1 + 10 ÷ 100) = 500 × 1.10
Step 1: 10% of 500 = 50
Step 2: 500 + 50 = 550
= 550

Example 5 – Decrease 80 by 25%

Original = 80, Decrease = 25%
80 × (1 − 0.25) = 80 × 0.75
Step 1: 25% of 80 = 20
Step 2: 80 − 20 = 60
= 60

Example 6 – Percentage change from 80 to 100

Original = 80, New = 100
((100 − 80) ÷ 80) × 100
Step 1: Difference = 100 − 80 = 20
Step 2: 20 ÷ 80 = 0.25
Step 3: 0.25 × 100 = 25
= 25% increase

Example 7 – Percentage difference between 70 and 85

Value 1 = 70, Value 2 = 85
|70 − 85| ÷ ((70 + 85) ÷ 2) × 100
Step 1: |70 − 85| = 15
Step 2: Average = 155 ÷ 2 = 77.5
Step 3: 15 ÷ 77.5 = 0.1935…
Step 4: × 100 ≈ 19.35%
≈ 19.35%

How to Find a Percentage – Percentage Finder Guide

How to find a percentage of a number

To find X% of any number Y: convert the percentage to a decimal by dividing by 100, then multiply. The formula is (X ÷ 100) × Y. Example: 35% of 60 = 0.35 × 60 = 21.

How to find what percent one number is of another

Divide the smaller number (the part) by the larger number (the whole), then multiply by 100. Formula: (Part ÷ Whole) × 100. Example: 18 out of 72 = (18 ÷ 72) × 100 = 25%.

How to find the original number from a percentage (reverse percentage)

If you know the part and the percentage it represents, divide the part by the percentage as a decimal. Formula: Whole = Part ÷ (P ÷ 100). Example: 45 is 30% of what? 45 ÷ 0.30 = 150.

How to calculate percentage increase or decrease

For percentage increase, subtract original from new, divide by original, multiply by 100: ((New − Old) ÷ Old) × 100. A positive result is an increase; negative is a decrease. To apply a percentage change to a value: New = Old × (1 + Rate ÷ 100).

Percentage Change vs. Percentage Difference — What's the Difference?

These two concepts are frequently confused. Understanding the distinction prevents calculation errors in real-world scenarios.

Percentage change

Use percentage change when one value is clearly the "before" (original) and the other is the "after" (new). The original value is the reference point (denominator). This is directional — you can have an increase or a decrease.

When to use it: price changes over time, salary before and after a raise, test scores improving, population growth.

Percentage difference

Use percentage difference when comparing two values where neither is the defined starting point. The formula uses the average of the two values as the denominator, making it symmetrical — the result is the same regardless of which value is listed first.

When to use it: comparing two different products, two exam scores from different students, two measurements where neither is the "original".

Key rule

If there's a clear before and after → use percentage change. If you're comparing two items side-by-side with no defined starting point → use percentage difference.

Everyday Uses for a Percentage Calculator

🛍️
Discounts & Sales
Find the sale price after 20%, 30%, or 50% off. Or find what percent off a deal actually is.
🧾
Tax & Tips
Calculate sales tax on a purchase or a 15–20% tip at a restaurant instantly.
📝
Exam Scores
Convert raw scores to percentages: 43 correct out of 55 questions = 78.2%.
🎓
GPA & Grades
Check your percentage grade in a course, or compare scores across different marking schemes.
💼
Salary Raises
Calculate the dollar amount of a 5% or 10% raise, or find what percentage raise you received.
📈
Investment Returns
Calculate how much your portfolio grew (or fell) as a percentage over any time period.
🏪
Profit Margins
Find gross margin: profit as a percentage of revenue. Essential for business pricing decisions.
🏥
Nutrition & Health
Calculate percent of daily values, body fat percentage changes, or progress toward health goals.

Common Percentage Mistakes to Avoid

  • Dividing by the wrong base. For percentage change, always divide by the original value, not the new one. Using the new value gives a different (incorrect) result.
  • Confusing percentage change with percentage difference. These use different denominators and are not interchangeable. See the section above for when to use each.
  • Forgetting to multiply by 100. After dividing part by whole, the result is a decimal (e.g., 0.25). Multiply by 100 to get the percentage (25%).
  • Mixing up "part" and "whole." The whole is the total; the part is the specific amount you're comparing. Swapping them inverts the percentage.
  • Applying sequential percentages incorrectly. A 20% increase followed by a 20% decrease does not return to the original. 100 → 120 → 96 (a 4% net loss).
  • Treating a percentage point change as a percentage change. Rising from 4% to 6% is a 2 percentage-point change but a 50% relative change. These mean different things.
  • Using percentage for absolute differences. When the original value is very small, percentage changes can appear misleadingly large. Always consider context.

Frequently Asked Questions

How do I calculate a percentage?
To calculate X% of a number Y: convert the percentage to a decimal (X ÷ 100), then multiply by Y. Formula: (X ÷ 100) × Y. Example: 20% of 150 = 0.20 × 150 = 30. Use the "X% of Y" tab above to calculate instantly.
How do I find what percent one number is of another?
Divide the part by the whole, then multiply by 100. Formula: (Part ÷ Whole) × 100. Example: 45 is what percent of 180? (45 ÷ 180) × 100 = 25%.
How do I calculate percentage increase?
Subtract the original value from the new value, divide by the original, and multiply by 100. Formula: ((New − Old) ÷ Old) × 100. Example: from 80 to 100: ((100 − 80) ÷ 80) × 100 = 25% increase.
How do I calculate percentage decrease?
Same formula as percentage change — when the new value is smaller than the original, the result is negative, indicating a decrease. Example: from 200 to 150: ((150 − 200) ÷ 200) × 100 = −25%, a 25% decrease.
What is percentage difference?
Percentage difference measures the relative difference between two values using their average as the denominator. Formula: |A − B| ÷ ((A + B) ÷ 2) × 100. It's used when neither value is the defined "original."
How do I find the original number from a percentage?
If X is P% of some number, the original = X ÷ (P ÷ 100). Example: 30 is 15% of what? 30 ÷ 0.15 = 200. Use the "X is P% of what?" tab above.
What is the percentage formula?
The core percentage formula is: Percentage = (Part ÷ Whole) × 100. The three rearrangements are: Part = (Percentage ÷ 100) × Whole; Whole = Part ÷ (Percentage ÷ 100); and Percentage = (Part ÷ Whole) × 100.
Can I calculate percentages online for free?
Yes. This percentage calculator is completely free, requires no sign-up, and works in any browser. It handles all six types of percentage calculations with instant results, formulas, and step-by-step solutions.
What is the difference between percentage change and percentage difference?
Percentage change has a defined starting point (the original) and measures how much it changed. Percentage difference has no defined starting point and uses the average of the two values as the denominator, making it symmetrical.
How do I increase a number by a percentage?
Multiply the original value by (1 + Percentage ÷ 100). Example: increase 400 by 15%: 400 × 1.15 = 460. Alternatively, calculate 15% of 400 = 60, then add: 400 + 60 = 460.
How do I decrease a number by a percentage?
Multiply by (1 − Percentage ÷ 100). Example: decrease 400 by 15%: 400 × 0.85 = 340. Or: find 15% of 400 = 60, then subtract: 400 − 60 = 340.
What is 1% of a number?
1% of any number = that number ÷ 100. For example, 1% of 850 = 8.5. This is useful for mental math: find 1%, then multiply to get any other percentage. Example: 7% of 850 = 8.5 × 7 = 59.5.
Is this percentage finder accurate?
Yes. Results use standard mathematical percentage formulas and are computed in JavaScript with IEEE 754 double-precision arithmetic, accurate to about 15 significant figures. Results are displayed rounded to 6 significant figures. For critical financial or academic calculations, verify independently.
How do I calculate a percentage on a calculator?
On a basic calculator: for X% of Y, enter Y × X ÷ 100 =. On most modern calculators, enter Y × X % =. This online percentage finder does all of it automatically — just enter your values and click Calculate.
What does percent mean?
Percent comes from the Latin per centum, meaning "per hundred." A percentage expresses a number as a fraction of 100. For example, 35% = 35/100 = 0.35. Any fraction can be converted to a percentage by multiplying by 100.

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Disclaimer: Results are based on standard mathematical percentage formulas. Percentage change and percentage difference are not the same calculation and should not be used interchangeably. For high-stakes financial, academic, or scientific decisions, verify results with a certified instrument or professional.
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