Percentage Calculator Guide

Use this percentage calculator when you need to find what percent one value is of another, calculate a part from a known whole and percentage, or estimate the whole from a part and percent. The calculator is useful for exam marks, discounts, profit margins, survey results, attendance, and quick classroom examples.

What Is a Percentage?

A percentage is a fraction out of 100. If a student scores 45 marks out of 60, the percentage is:

(45 / 60) x 100 = 75%

How to Use This Calculator

Select the percentage mode that matches your question.
Enter the values you already know.
Click Calculate.
Check the result and working details before rounding.

Common Percentage Formulas

Percentage = (part / whole) x 100
Part = (percentage / 100) x whole
Whole = part / (percentage / 100)

Worked Examples

Example 1: What percent is 30 of 150?

(30 / 150) x 100 = 20%

Example 2: What is 15% of 240?

(15 / 100) x 240 = 36

Example 3: 18 is 12% of what number?

18 / 0.12 = 150

Mistakes to Avoid

Do not divide by zero when the whole value is unknown or empty. Also remember that percentage points and percentage change are different ideas: moving from 40% to 50% is a 10 percentage-point increase, not simply a 10% increase.

Important Note

Round according to the context. For exam marks, one or two decimal places is usually enough. For finance or tax calculations, use the rounding rule required by the form or institution.

Frequently Asked Questions

How do I calculate a percentage from marks?

Divide obtained marks by total marks and multiply by 100.

Can this calculator find the original whole?

Yes. Choose the mode that finds the whole from a known part and percentage.

What does 25% mean?

25% means 25 out of 100, or one quarter of the whole.

Is percentage always out of 100?

Yes. A percentage expresses a value as a share of 100.

Percentage Calculator