css relative units code example

Example 1: css em

em -> Relative to the font-size of the element 
(2em means 2 times the size of the current font)

Example 2: em css

/*realative to the font-size*/

Example 3: pixels and em mdn

html { 
  font-size: 62.5%; /* font-size 1em = 10px on default browser settings */ 
} 
span { 
  font-size: 1.6em; 
}