css calc font size
/*Here a possible solution:*/
http://codepen.io/CrocoDillon/pen/fBJxu
p {
margin: 0;
font-size: calc(4vw + 4vh + 2vmin);
/* See:
* http://codepen.io/CrocoDillon/pen/jgmwt
* For some math behind this
*/
}
/*Font-size is calculated with available size using a function that is not
perfect, but may be adjusted to work well in some cases.*/