What Does Box Sizing Border Box Do In Css

CSS Programming

When it comes to CSS, one of the most important properties to understand is box-sizing. This property determines how the width and height of an element are calculated, taking into account the element’s padding and border.

By default, the box-sizing property is set to content-box. This means that the width and height of an element only include the content of the element, and do not take into account the padding or border. This can sometimes lead to unexpected layout issues, especially when working with elements that have padding or border styles applied.

That’s where box-sizing: border-box comes in. When you set the value of box-sizing to border-box, the width and height of the element will include the content, padding, and border. This ensures that the overall dimensions of the element remain consistent regardless of any padding or border applied.

For example, let’s say you have a <div> element with a width of 200px and a padding of 20px. With the default content-box value, the total width of the element would be 240px (200px for content + 20px left padding + 20px right padding). However, if you set box-sizing: border-box, the total width of the element would be 200px, as the padding is included in the calculation.

Using box-sizing: border-box can be particularly useful when working with responsive designs or grid systems. It allows you to more easily control the overall size and spacing of elements, without constantly adjusting for padding or border widths.

Personally, I find box-sizing: border-box to be a real game-changer when it comes to CSS layouts. It simplifies the way I think about element sizing and helps me avoid those pesky layout issues that can arise from the default content-box behavior.

It’s worth mentioning that box-sizing is not supported in older versions of Internet Explorer, specifically versions 7 and below. However, with the decline in usage of these older browsers, it’s becoming less of a concern.

So, the next time you’re working on a CSS layout, consider using box-sizing: border-box to simplify your element sizing and make your life a little easier.