Understanding Percentages
A percentage is a mathematical way of expressing a number as a fraction of 100. It is widely used in finance, retail, statistics, and daily life to make comparing ratios simple and intuitive. The word "percent" comes from the Latin per centum, meaning "by a hundred."
How to Calculate Percentages
Depending on what you are trying to find, there are three primary formulas you will use:
1. What is X% of Y?
To find a specific percentage of a whole number, convert the percentage to a decimal (divide by 100) and multiply by the total.
Formula: (X / 100) × Y
Example: What is 25% of 200? (25 / 100) × 200 = 50.
2. X is what % of Y?
To find what percentage one number represents compared to another, divide the part by the whole and multiply by 100.
Formula: (X / Y) × 100
Example: 50 is what percent of 200? (50 / 200) × 100 = 25%.
3. Percentage Change (Increase / Decrease)
To calculate how much a value has changed as a percentage of its original state, subtract the old value from the new value, divide by the old value, and multiply by 100.
Formula: ((New Value - Old Value) / Old Value) × 100
Example: If a stock goes from $100 to $125, what is the percentage change? ((125 - 100) / 100) × 100 = +25%.