How to use Percentage Calculator
- Choose a percentage calculation from the menu.
- Enter A and B using the labels and formula shown.
- Your result appears automatically when both numbers are valid. Change either number to update it, or clear the values to start again.
A closer look
Answer three common percentage questions in one place. “A% of B” multiplies B by A/100. “A is what percent of B” divides A by B and multiplies by 100. Percentage change from B to A uses (A − B) / |B| × 100, so the sign indicates an increase or decrease even when the base is negative.
A practical example
15% of 200 is 30. To measure a change from 100 to 120, choose percentage change, set the base to 100 and the new value to 120: the increase is 20%.
A useful tip
A zero base cannot define a proportion or percentage change. Results are rounded for display to 12 significant digits and should be checked when exact accounting precision is required.
Good questions. Simple answers.
What is the difference between percent and percentage points?
Moving from 20% to 30% is a 10 percentage-point increase and a 50% relative increase. This tool calculates relative percentages, not percentage-point differences.
Can I use negative values?
Yes. For percentage change, the denominator is the absolute value of the base B. This convention is stated here because negative bases can be interpreted differently in other contexts.
Explore all calculators for related tasks and category-specific guidance, or read how Toolzafi handles your data.