if you looking for a nice scale google docs looks like they have a nice scale and they use these:

:root { font-size: 14px; }
h1{font-size:2rem;}
h2{font-size:1.6rem;}
h3{font-size:1.4rem;}
h4{font-size:1.2rem;}
h5{font-size:1.1rem;}
h6{font-size:1.1rem;font-style: italic;}