box-sizing 告诉浏览器如何计算一个元素的总宽度和总高度
语法
box-sizing: content-box|border-box|inherit:
1、content-box: W3C标准盒模型
[扩展] 内容尺寸不变，总尺寸增加
total = content + border + padding
2、border-box: IE怪异盒模型
[压缩] 总尺寸不变，内容尺寸减少
content = total - border - padding;
计算示例
<style type="text/css">
* {
margin: 0;
padding: 0;
}
.box {
width: 200px;
height: 100px;
padding: 20px;
border: 10px solid red;
background:yellow;
}
.content-box {
box-sizing: content-box;
}
.border-box {
box-sizing: border-box;
}
</style>
<body>
<div class="box">box</div>
<div class="box content-box">content-box</div>
<div class="box border-box">border-box</div>
</body>
计算方式
1、box-sizing: content-box
Total width: 200px + (2 * 20px) + (2 * 10px) = 260px
Total height: 100px + (2 * 20px) + (2 * 10px) = 160px
Content box width: 200px
Content box height: 100px
2、box-sizing: border-box
Total width: 200px
Total height: 100px
Content box width: 200px - (2 * 20px) - (2 * 10px) = 140px
Content box height: 100px - (2 * 20px) - (2 * 10px) = 40px
参考
MDN-box-sizing菜鸟教程-CSS3 box-sizing 属性
