Percentage Calculator Notes

Calculator Use

• Calculate percentages or find unknowns using percentage formulas.
• Add or subtract percentages from numbers.

How to Calculate Percentages

• Basic formula: X/Y = P x 100
• Three fundamental problems:
  1. Find P percent of X
  2. Determine what percent of X is Y
  3. Find X if P percent of it is Y

1. Calculate Percentage of a Number

• Formula: P% * X = Y
• Example: What is 10% of 150?
  • Convert percentage: 10% to 0.10 (10/100)
  • Equation: 0.10 * 150 = 15
  • Result: 10% of 150 is 15

2. Find What Percent of X is Y

• Formula: Y/X = P%
• Example: What percent of 60 is 12?
  • Equation: 12/60 = 0.20
  • Convert to percent: 0.20 * 100 = 20%
  • Result: 20% of 60 is 12

3. Find X if P Percent of it is Y

• Formula: Y/P% = X
• Example: 25 is 20% of what number?
  • Convert percentage: 20% to 0.20
  • Equation: 25/0.20 = 125
  • Result: 25 is 20% of 125

Conversion Reminders

• Percentage to Decimal: Remove % and divide by 100
• Decimal to Percentage: Multiply by 100 and add %

Percentage Problems Variations

• Nine variations based on three basic problems.
  • Match problems to sample formats.

Example Problems

• What is P percent of X?
  • Formula: Y = P% * X
  • Example: What is 10% of 25? Result: 2.5
• Y is what percent of X?
  • Formula: P% = Y/X
  • Example: 12 is what percent of 40? Result: 30%
• Y is P percent of what?
  • Formula: X = Y/P%
  • Example: 9 is 60% of what? Result: 15
• Other examples with various combinations provided.

Related Calculators

• Percentage Change Calculator: Find increase or decrease percentage.
• Decimal to Percent Calculator: Convert decimals to percentage.
• Percent to Decimal Calculator: Convert percentage to decimals.
• Fraction to Percent Calculator: Convert fractions to percentages.
• Percent to Fraction Calculator: Convert percentages to fractions.

References

• Eric W. Weisstein's "Percent" from MathWorld, a Wolfram Web Resource.