The Box Model

Everything on the Internet is basically a bunch of boxes. Whether we see them or not, they're there. So here we discuss the box model.

Explanation of the different parts:

Content - The content of the box, where text and images appear
Padding - Clears an area around the content. The padding is transparent
Border - A border that goes around the padding and content
Margin - Clears an area outside the border. The margin is transparent

The box model allows us to add a border around elements, and to define space between elements. Code from the "Try it yourself" section.

Width and Height of an Element

In order to set the width and height of an element correctly in all browsers, you need to know how the box model works.

Important: When you set the width and height properties of an element with CSS, you just set the width and height of the content area. To calculate the full size of an element, you must also add padding, borders and margins.

Example

This div element will have a total width of 350px:

Next example of the box model. Gray box. Some extra text to see the text wraps in a 350px width box.

Here is the calculation:

350px (width)

+ 20px (left + right padding)

+ 10px (left + right border)

+ 40px (left + right margin)

= 420px

The total width of an element should be calculated like this:

Total element width = width + left padding + right padding + left border + right border + left margin + right margin

The total height of an element should be calculated like this:

Total element height = height + top padding + bottom padding + top border + bottom border + top margin + bottom margin

The CSS Box Model

In CSS, the term "box model" is used when talking about design and layout.