CSS Box Model
All HTML elements can be considered as boxes.
The CSS Box Model
In CSS, the term "box model" is used when talking about design and layout.
The CSS box model is essentially a box that wraps around every HTML element.
It consists of: margins, borders, padding, and the actual content. The image below illustrates 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.
Example
Demonstration of the box model:
div { width: 300px; border: 15px solid
green;
padding: 50px;
margin: 20px;}
Try it Yourself »
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:
div {
width: 320px;
padding: 10px;
border: 5px solid gray;
margin: 0;
}
Try it Yourself »
Here is the calculation:
320px (width)
+ 20px (left + right padding)
+ 10px (left + right border)
+ 0px (left + right margin)
= 350px
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
Test Yourself With Exercises
Exercise:
Set the width of the <div> element to "200px".
<style>
{
: ;
}
</style>
<body>
<div>
Lorem ipsum dolor sit amet,
consectetur adipiscing elit,
sed do eiusmod tempor incididunt
ut labore et dolore magna aliqua.
</div>
</body>
Submit Answer »
Start the Exercise
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Reference: https://www.w3schools.com/css/css_boxmodel.asp