<div class="box">
  Lorem ipsum dolor sit amet.
</div>
// * {
//  box-sizing: border-box;
// }

/**打開 box-sizing 的註解，使用開發人工具的檢查，看一下尺寸的變化*/

.box {
  width: 100px;
  height: 100px;
  background-color: red;
  padding: 10px;
  color: #fff;
}
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