How percentages are calculated

This tool covers the three most common percentage calculations: finding X% of a number (multiply by the percentage, divide by 100), percentage change between two values (the difference divided by the absolute starting value, times 100), and what percentage one number is of another (divide the part by the whole, times 100).

How to use this percentage calculator (also called a percent or % calculator)

1. Pick the calculation you need: X% of Y, percentage change, or „X is what % of Y“.
2. Enter your numbers.
3. Click Calculate for an instant result.

Example: 20% of 150 is 30. Going from 50 to 75 is a +50% change.

Where percentages show up in everyday life

Percentages appear constantly outside the classroom: calculating a restaurant tip, figuring out a sale discount, comparing interest rates, tracking a pay raise, or reading statistics in the news. Because the underlying math is always one of the same three operations — finding a part of a whole, comparing two values, or expressing one number relative to another — a single calculator can cover almost every situation you’ll run into.

Percentage change vs. percentage points

A common source of confusion is mixing up percentage change with percentage points. If an interest rate moves from 5% to 7%, that’s a 2 percentage point increase, but a 40% percentage change (2 divided by 5, times 100). Financial news and statistics often use these interchangeably, so it’s worth checking which one is actually meant.

Tips for working with percentages

When comparing two percentage changes, always check whether they’re measured from the same starting point — a 10% increase followed by a 10% decrease does not return you to the original value, since the second change applies to a larger or smaller base. For discounts, remember that a 50% off followed by an additional 20% off is not a 70% total discount — it’s 60%, since the second discount applies to the already-reduced price.

Expert insight: the method behind every percentage problem

Khan Academy’s approach to percentages, used by millions of students, boils every version of the problem down to one method: write it as a fraction, then convert that fraction so the denominator is 100 (or divide and multiply by 100 to get the same result as a decimal). Once percentage change and „part of a whole“ are seen as the same underlying fraction-to-100 conversion, the different phrasings of percentage word problems stop feeling like separate topics.

Related calculators

• Grade Calculator
• Fraction Calculator
• Unit Converter