08. Box Sizing

The default selection for a CSS box is just the box's content, without the padding and border. Consequently, if you define the height and width, it'll only pertain to the box's content area.

If you'd like to specify that the content includes the padding and border, we use the box-sizing property with a border-box value. The default value is content-box.

#box1, #box2 {
  border: 1px solid black;
  border-radius: 10px;
  text-align: center;
  padding: 10px;
  height: 50%;
  width: 50%;
  margin: 10px auto;
}
  
#box1 {
  box-sizing: content-box;
}
  
#box2 {
  box-sizing: border-box;
} 
This is box 1.
This is box 2.

Notice how the first box is bigger, since the height applied only applies to the content area.

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