Percentage Calculator
The three percentage questions people actually ask — each with its own formula.
System verdict
RESULT15% of 200 = 30
To find a percentage of a number, multiply the number by the percentage over 100.
Diagnostic telemetry
- Result
- 30
What this cannot tell you
- Pure arithmetic on the values you enter.
How this calculation works
Pick the question you are asking, because each is a different formula. "A% of B" multiplies B by A/100. "A is what percent of B" divides A by B. "Percent change" takes the difference over the starting value.
What the results mean
- A% of B
- A slice of a whole — 15% of 200 is 30.
- A is what % of B
- A as a proportion — 30 out of 200 is 15%.
- Percent change
- Growth or decline relative to the start. From 200 to 230 is +15%; the base is always the starting value.
Frequently asked questions
Why is percent change measured against the starting value?
Because change is relative to where you began. A rise from 100 to 150 is +50%, but the reverse — 150 back to 100 — is only −33%, because the base is different each time. That asymmetry surprises people, and it is why the starting value, not the average, is the denominator.