Percentage Calculator
Percentage of a value, share of a total, or percent change.
Percentage
Of Value
Result
30.00
20% of 150 is 30
How this calculator works
Each mode is a rearrangement of the same relationship between a part, a whole, and a percentage. "X% of Y" multiplies Y by X÷100. "X is what % of Y" divides X by Y and multiplies by 100. "% Change" takes the difference between two values as a fraction of the starting value, so it correctly shows a decrease as negative.
Why percent change isn't symmetric
Percent change is the one people most often get wrong by hand — going from 50 to 75 is a 50% increase, but going from 75 back to 50 is only a 33.3% decrease, because the base you're dividing by is different each time (75 the first time, 50 the second). A value can never "undo" an X% increase by dropping the same X% — it takes a slightly smaller percentage decrease to get back to where it started.
Percentage points vs. percent
These sound interchangeable but aren't. If an interest rate moves from 5% to 7%, that's a 2 percentage point increase — but it's a 40% relative increase (2 ÷ 5 × 100). News headlines often blur this distinction; knowing which one you're looking at matters a lot when the numbers involved are large.
Frequently Asked Questions
How do I calculate a percentage of a number?
Multiply the number by the percentage, then divide by 100 — for example, 20% of 150 is (150 × 20) / 100 = 30. This calculator handles that along with percentage change and "what percent is X of Y" calculations.
How is percentage change calculated?
Percentage change is ((new value − old value) / old value) × 100 — a positive result is an increase, a negative result is a decrease.
What's the difference between percentage points and percent?
Percentage points measure the absolute difference between two percentages (e.g., going from 20% to 25% is a 5 percentage point increase), while percent change measures the relative difference (that same move is a 25% increase relative to the original 20%).
If something increases 50%, does decreasing it 50% get back to the original?
No — going from 50 to 75 is a 50% increase, but going from 75 back to 50 is only a 33.3% decrease, because percent change is always relative to the current starting value, and that value is different in each direction.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100 — for example, 30 is what percent of 150? (30 / 150) × 100 = 20%. This calculator includes that mode alongside percentage-of and percentage-change.