change font size of h1 in html

1Default font-size
2
3h1 ---> 32px   (2em)
4h2 ---> 24px (1.5em)
5h3 ---> 20.8px (1.3em)
6h4 ---> 16px   (1em)
7h5 ---> 12.8px (0.8em)
8h6 ---> 11.2px (0.7em)

1<span style="font-size:20px;"></span>

1font-size: 25px;

1<style>
2h1 { 
3	font-size: 100px;
4   }
5</style>