Is the border thickness added to the box height and width?

Question

Is the border thickness added to the box height and width?

Answer

It is important to realize that there is a distinction between the rendered height and width of an element and the width and height properties of an element. By default, the width and height properties only affect the content area of a box. This means that while the border, padding, and margin properties do affect the rendered dimensions of an element they do not factor into the width and height of a box’s content area as specified by the width and height properties.

As you will learn in the next lesson, this default behavior can be modified with the box-sizing: border-box; declaration.