box-sizing

by rootjang

HTML

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
</head>
<body>
  <div class="box1"> content-box </div>
  <div class="box2"> border-box </div>
</body>
</html>

CSS

.box1 {
  box-sizing: content-box;
  width: 300px;
  height: 150px;
  margin: 10px;
  padding: 30px;
  border: 2px solid red;
}

.box2 {
  box-sizing: border-box;
  width: 300px;
  height: 150px;
  margin: 10px;
  padding: 30px;
  border: 2px solid red;
}