盒子规格Box-sizing

html

<div class="box">border-box</div>
<div class="box content-box">content-box</div>

CSS

html {
  box-sizing: border-box;
}
*,
*::before,
*::after {
  box-sizing: inherit;
}
.box {
  display: inline-block;
  width: 150px;
  height: 150px;
  padding: 10px;
  background: tomato;
  color: white;
  border: 10px solid red;
}
.content-box {
  box-sizing: content-box;
}

关键点:
box-sizing :

1. content-box: 默认, 指定元素内容的宽度和高度
2. border-box: 增加padding 和 border 都不影响元素的宽高
3. inherit: 该元素继承父元素的box-sizing