How this calculator works
A percent is a fraction with a denominator of 100. Each question uses a different denominator, so choose the question before entering numbers. Percentage change uses a positive starting value here to keep increases and decreases unambiguous.
Formula
X% of Y = (X/100) × Y. X as a percentage of Y = (X/Y) × 100%. Percentage change = ((Y - X)/X) × 100%.
Worked example
20% of 200 is 40. A part of 50 out of 200 is 25%. An increase from 120 to 150 is 25%; a decrease from 80 to 60 is -25%.
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Frequently asked questions
Why can the total not be zero?
A part divided by a zero total has no defined percentage. For change, a zero original value also gives an undefined denominator.
Is percentage change the same as percentage points?
No. Moving from 20% to 25% is an increase of 5 percentage points. Relative to the starting 20%, it is a 25% increase.
Can the answer be more than 100%?
Yes. In the question that expresses X as a percentage of Y, a value of X larger than Y gives a result above 100%.