Why Do Percentage Heights in CSS Behave Differently Than Percentage Widths?

Why Percentage Height Differs from Width in CSS

Question: Despite the successful application of percentage values for width, why do percentage heights fail to achieve the same effect?

Answer: The fundamental distinction lies in the default behavior of block elements. The height of these elements inherently adapts to the content they enclose. consider the following example:

<div>

Here, #inner will expand vertically to accommodate the text within the

, and #outer will adjust its height to contain #inner.

When specifying a percentage height or width, it refers to the parent element. For width, block elements typically span the full width of their parent, making the result predictable. Setting width: 50% translates to a specific pixel width.

However, height differs as block element heights are determined by content. Assigning height: 50% is ambiguous without explicitly defining the parent element's height. This feedback loop between parent and child elements creates uncertainty in determining the final height. To break this cycle, the parent element must possess a specified height.

The above is the detailed content of Why Do Percentage Heights in CSS Behave Differently Than Percentage Widths?. For more information, please follow other related articles on the PHP Chinese website!