box model

Total width = left margin + left border + left padding + width + right padding + right border + right margin

Total width = 15 + 1 + 10 + 300 + 10 + 1 + 15 = 352px

Total height = 15 + 1 + 10 + 200 + 10 + 1 + 15 = 252px

.box {
  width: 300px;
  height: 200px;
  padding: 10px; /* padding: 10px 15px || padding: 10px 1px 18px 4px || padding: 10px 0 15px */
  border: 1px solid #000;
  margin: 15px;
}