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Percentage Calculator

Calculate percentages, increases, decreases, and more.

What is X% of Y?

Calculate what value represents a certain percentage of another number

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Common Examples:
X is what % of Y?

Find what percentage one number is of another

Common Examples:
Percentage Change

Calculate the percentage change from one value to another

Common Examples:
Increase or Decrease by Percentage

Calculate the result after increasing or decreasing by a percentage

%
Common Examples:
X is Y% of what?

Find the original value when you know the percentage and result

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Common Examples:
📚 How It Works
Basic Percentage Formula

Percentage means "per hundred" (from Latin "per centum"):

Percentage = (Part / Whole) × 100

Common Percentage Calculations
What is X% of Y?

Result = (X / 100) × Y

Example: 25% of 200 = (25/100) × 200 = 50

X is what % of Y?

% = (X / Y) × 100

Example: 50 is what % of 200? = (50/200) × 100 = 25%

Percentage Change

% Change = [(New - Old) / Old] × 100

Example: $100 → $125 = [(125-100)/100] × 100 = 25% increase

Increase/Decrease by %

Result = Original × (1 ± X/100)

Example: $100 + 20% = 100 × 1.20 = $120

X is Y% of what?

Whole = X / (Y / 100)

Example: 50 is 25% of what? = 50 / 0.25 = 200

Percentage vs. Percentage Points

Important distinction:

  • Percentage change: From 40% to 50% is a 25% increase [(50-40)/40 × 100]
  • Percentage point change: From 40% to 50% is a 10 percentage point increase [50-40]
Real-World Applications
  • Shopping: Discount calculations (25% off $80 = $20 discount, pay $60)
  • Finance: Interest rates, investment returns, inflation
  • Restaurants: Tips (15-20% of bill)
  • Taxes: Sales tax, income tax percentages
  • Statistics: Margins of error, confidence levels
  • Business: Profit margins, growth rates, market share
  • Education: Test scores, grade percentages
  • Health: Body fat percentage, concentration levels
Common Percentages to Remember
Percentage Decimal Fraction Quick Tip
100% 1.0 1/1 The whole amount
50% 0.5 1/2 Half
25% 0.25 1/4 Quarter
75% 0.75 3/4 Three quarters
10% 0.1 1/10 Move decimal left once
20% 0.2 1/5 Double 10%
33.33% 0.333... 1/3 One third
Mental Math Tricks
  • 10%: Move decimal point left one place (10% of 250 = 25)
  • 5%: Half of 10% (5% of 250 = 12.5)
  • 15%: 10% + 5% (useful for tips)
  • 20%: Double 10% (20% of 250 = 50)
  • 25%: Divide by 4 (25% of 80 = 20)
  • 50%: Divide by 2 (50% of 80 = 40)
🔗 Related Tools
Mean, Median, Mode Standard Deviation Variance Correlation
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