Practical guide
Percentage of a number, ratio and percentage change — how do they differ?
“Percentage” can mean part of a number, a relationship between values or change over time. Each question uses a different formula and assigns different roles to A and B.
Percentage of a number
To find A% of B, convert the percentage into A ÷ 100 and multiply by B. The result has the same unit as B.
For example, 15% of PLN 200 is PLN 30.
One value as a percentage of another
The question “A is what percentage of B” uses B as denominator: A ÷ B × 100%. B cannot be zero.
If 30 people from a group of 120 selected an answer, the share is 25%.
Percentage change
Change compares B − A with starting value A. Growth from 100 to 120 is 20%, but decline from 120 to 100 is about 16.67%.
Percentage points describe a difference between percentage values and are not the same as percentage change.
Frequently asked questions
What does this guide explain about “Percentage of a number”?
To find A% of B, convert the percentage into A ÷ 100 and multiply by B. The result has the same unit as B. For example, 15% of PLN 200 is PLN 30.
What does this guide explain about “One value as a percentage of another”?
The question “A is what percentage of B” uses B as denominator: A ÷ B × 100%. B cannot be zero. If 30 people from a group of 120 selected an answer, the share is 25%.
What does this guide explain about “Percentage change”?
Change compares B − A with starting value A. Growth from 100 to 120 is 20%, but decline from 120 to 100 is about 16.67%. Percentage points describe a difference between percentage values and are not the same as percentage change.
Calculators covered by this guide
Percentage calculator
Calculate a percentage of a number, percentage ratio or percentage change.