CSS Box-Sizing

Understanding CSS Box-Sizing

The box-sizing property in CSS defines how the total width and height of an element are calculated. It affects the dimensions of the box model, which includes content, padding, border, and margin. By default, elements use the content-box value, but you can change this to border-box for more intuitive layout management.

Values of Box-Sizing

CSS box-sizing can have the following values:

• content-box: This is the default value. The width and height properties include only the content, and padding and border are added outside the box.
• border-box: The width and height properties include content, padding, and border, making the box-sizing more intuitive for layout design.

Using content-box

When using content-box, the width and height you set only apply to the content, while padding and border are added to the outside. This can sometimes lead to confusion when laying out elements.

In this example, the total width of the element will be 250px (content width 200px + padding 20px on each side + border 5px on each side).

Using border-box

With border-box, the width and height you set include content, padding, and border. This simplifies the calculation of an element's total width and height, making layouts easier to manage.

In this case, the total width remains 200px because the padding and border are included within the width and height specified.

Global Reset with Box-Sizing

It's common practice to apply a global reset to ensure all elements use the border-box model. This can prevent layout issues and make design more consistent.

By applying this CSS rule, you ensure that every element on the page uses the border-box model, which can simplify layout calculations and improve design consistency.