# What Data Type Is Percentage?

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Angela Bailey

In HTML, the data type for representing a percentage is number. A percentage is a value that represents a proportion or fraction of 100.

It is commonly used to express relative values or rates of change. To understand how percentages are used in HTML, let’s take a closer look at how they can be applied in different contexts.

## Using Percentages in CSS

CSS (Cascading Style Sheets) is the language used to style and format web documents written in HTML. Percentages play an essential role when it comes to defining dimensions and positioning elements on a webpage.

For example, you can use percentages to specify the width and height of an element relative to its parent container. This allows your webpage to adapt and respond to different screen sizes and devices.

### Defining Width and Height

To set the width of an element using a percentage, you can use the CSS width property. For instance:

``<div style="width: 50%;">This div will take up 50% of its parent container's width.</div>``

The height property works similarly:

``<div style="height: 75%;">This div will take up 75% of its parent container's height.</div>``

### Positioning Elements

In addition to defining dimensions, percentages can also be used for positioning elements on a webpage. The CSS top, bottom, left, and right properties accept percentage values when positioning elements using absolute or relative positioning.

``<div style="position: absolute; top: 25%; left: 50%;">This div will be positioned 25% from the top and 50% from the left of its closest positioned ancestor.</div>``

## Using Percentages in JavaScript

In JavaScript, percentages are often used in calculations or to represent values based on a percentage scale. For example, you might use percentages to calculate discounts, progress bars, or dynamic changes based on user input.

### Calculating Percentages

JavaScript provides built-in functions to perform mathematical operations involving percentages. The parseFloat() function can be used to extract the numerical value from a percentage string:

``````const percentageString = "50%";
const numericValue = parseFloat(percentageString);
console.log(numericValue); // Output: 50``````

You can also use percentages to dynamically update elements on a webpage. For instance, you might change the width of a progress bar based on user input:

``````// Assuming 'progress' is an HTML element representing the progress bar
const inputElement = document.querySelector("input");