Percentage Calculator
Three calculators in one: find what a percentage of a number is, find what percentage one number represents of another, or find the percent change between two values.
How to use
“What is X% of Y” — e.g. what is 15% of 80: 15% × 80 = 0.15 × 80 = 12. Used for discounts, tips, taxes and commissions.
“A is what percent of B” — e.g. 12 is what percent of 80: (12 ÷ 80) × 100 = 15%. Used for grades, completion rates and proportions.
“Percent change from A to B” — e.g. from 80 to 92: ((92 − 80) ÷ 80) × 100 = +15%. A positive result is an increase, negative is a decrease. Used for price changes, growth rates and performance comparisons.
FAQ
How do I calculate a percentage of a number?
Multiply the number by the percentage divided by 100: X% of Y = (X / 100) × Y. For 20% of 150: (20/100) × 150 = 30.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100: (A / B) × 100. If 45 out of 60 questions were correct: (45/60) × 100 = 75%.
How is percent increase or decrease calculated?
((New value − Old value) / Old value) × 100. A price moving from $80 to $100 is a (100−80)/80 × 100 = 25% increase. From $100 to $80 is a −20% change (a decrease), not the mirror +20% — percent change is never symmetric.
Why isn't a 20% increase undone by a 20% decrease?
Because each percentage applies to a different base. $100 up 20% is $120; $120 down 20% is $96, not $100 — you're taking 20% of a larger number on the way down. This is a common source of pricing and discount confusion.