What are the size units of css?

There are many types of size units in CSS, and each unit has its applicable scenarios and uses. The following will introduce the commonly used CSS size units in detail and provide corresponding code examples.

1. Pixels (px)
   Pixels are one of the most commonly used units of size. It is measured relative to the physical pixels of the screen and has a fixed size. When writing CSS styles, you can directly use pixels as values ​​for properties such as width, height, borders, and inner and outer margins. For example:

   div {
     width: 200px;
     height: 100px;
     border: 1px solid #000;
     padding: 10px;
     margin: 20px;
   }

2. Percent (%)
   Percent is a unit of measurement relative to the size of the parent element. It can be used for attributes such as width, height, inner and outer margins, and borders. By setting the percentage, you can achieve responsive layout. For example:

   div {
     width: 50%;
     height: 50%;
   }

3. em
   em is a unit of measurement relative to the font size of the current element. If the font size is not set explicitly, the size in em units is equal to the font size of the parent element. It can be used for attributes such as width, height, inner and outer margins, and borders. For example:

   div {
     width: 2em;
     height: 2em;
     padding: 1em;
     border: 0.5em solid #000;
   }

4. rem
   rem is a unit of measurement relative to the font size of the root element (that is, the html element). It can be used for attributes such as width, height, inner and outer margins, and borders. Global size control can be achieved by setting the font size of the root element. For example:

   html {
     font-size: 16px; /* 设置根元素的字体大小为16px */
   }
   div {
     width: 20rem;
     height: 10rem;
     padding: 4rem;
     border: 2rem solid #000;
   }

5. vw and vh
   vw is a percentage of the viewport width and vh is a percentage of the viewport height. They are measured relative to the dimensions of the browser viewport. They can be used for properties such as width, height, etc. By setting vw and vh, responsive layout can be achieved. For example:

   div {
     width: 50vw; /* 视口宽度的50% */
     height: 50vh; /* 视口高度的50% */
   }

Summary:
This article introduces the commonly used size units of CSS, including pixels, percentages, em, rem, vw and vh. Reasonable selection and use of size units can make web pages adaptable and responsive. In actual development, selecting appropriate units for setting according to specific needs and scenarios can make the layout of the page more flexible and beautiful.

The above is the detailed content of What are the size units of css?. For more information, please follow other related articles on the PHP Chinese website!