Percentage Calculator

Percentage Calculator - Three Essential Calculations

This tool helps you quickly solve three common percentage problems: finding a percentage of a number, determining what percent one number is of another, and calculating the percentage change between two values. It's useful for students, shoppers, and anyone working with ratios and proportions in everyday math.

How to use this calculator

  1. Choose the type of calculation you need: percentage of a number, percent of another number, or percentage change.
  2. Enter the required numbers in the input fields. For example, for percentage of a number, enter the percentage and the number.
  3. The result will update automatically as you type. No need to press a button.
  4. For percentage change, enter the old value and the new value; the tool will show the increase or decrease.
  5. Use the clear button if you want to reset the inputs.

Common questions

What is a percentage?

A percentage is a number or ratio expressed as a fraction of 100. It is often denoted using the percent sign, "%".

How do I calculate a percentage of a number?

Multiply the number by the percentage and then divide by 100. For example, 25% of 80 is (25 × 80) / 100 = 20.

What is the formula for percentage change?

Percentage change = ((new value - old value) / old value) × 100. A positive result indicates an increase, while a negative result indicates a decrease.

Can I use decimals or negative numbers?

Yes, the calculator accepts decimals and negative numbers. For percentage change, if the old value is zero, the change is undefined, so the tool will show an error message.

Why do I get an error when I enter zero for the whole in "what percent" calculation?

Dividing by zero is not allowed in mathematics. The "whole" must be a non-zero number to calculate what percent one number is of another.