Statistics
Percentage calculator
The three percentage questions that come up in real life — a share of a total, a part as a percent, and the change between two numbers — each with the answer as you type.
12
15%
+25%increase
The three questions, one page
Almost every everyday percentage problem is one of three shapes: what is X% of Y (a tip, a discount, a tax), X is what percent of Y (a score, a share), and the percentage change from A to B (a raise, a price move). Once you can spot which one you’re facing, the arithmetic is easy.
Where percentages trip people up
A 50% drop followed by a 50% rise doesn’t return you to the start — it leaves you 25% down, because the second 50% is taken from a smaller number. Percentages always need a base, and forgetting which base you’re using is where most mistakes hide.
Read the numbers with confidence
Percentages are everywhere in headlines and charts. The Statistics subject shows how to read them critically, and the statistics glossary defines the terms that go with them.
Frequently asked questions
- How do I calculate a percentage of a number?
- Divide the percentage by 100 and multiply by the number. For example, 15% of 80 is 0.15 × 80 = 12. The first box does this for you.
- How do I find what percent one number is of another?
- Divide the part by the whole and multiply by 100. So 12 out of 80 is (12 ÷ 80) × 100 = 15%. The second box handles this.
- How do I calculate percentage increase or decrease?
- Subtract the old value from the new value, divide by the old value, and multiply by 100. Going from 80 to 100 is ((100 − 80) ÷ 80) × 100 = +25%. A negative result means a decrease.
- What’s the difference between percentage points and percent?
- A change from 40% to 44% is a rise of 4 percentage points, but a 10% increase in relative terms. Mixing the two is one of the most common ways statistics mislead — worth keeping straight.