Everyday math
Percentage calculator
Solve three common percentage questions: part of a whole, percentage change, and percent ratios.
Calculate a percentage
Choose the question that matches what you need.
Result
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Percentage formulas
X% of Y = (X ÷ 100) × Y
Percentage change = (new − original) ÷ |original| × 100
Part as a percent of whole = part ÷ whole × 100
Percentage change = (new − original) ÷ |original| × 100
Part as a percent of whole = part ÷ whole × 100
Example
A price rising from $80 to $100 increased by $20. Divide $20 by the original $80 and multiply by 100: the increase is 25%.
A common mistake
Percentage change uses the original value as the denominator. Reversing the starting and ending values produces a different percentage because it answers a different question.
Method reviewed September 25, 2026. See our calculation methodology.