When I set border-box to input without a specific height and width, padding increases the width of the input. On the other hand, if I do the same, but with a established size, then it works as normal as on a regular div, setting the padding without changing the width of the input.
Short snippet
#input1 {
box-sizing: border-box;
padding: 0 10px;
}
#input2 {
width: 200px;
height: 30px;
box-sizing: border-box;
padding: 0 50px;
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=">
<title></title>
</head>
<body>
input1: <input type="text" name="text" id="input1"> <br/><br/>
input2: <input type="text" name="text" id="input2">
</body>
</html>