You can use viewport value instead of ems, pxs or pts.
1vw = 1% of viewport width
1vh = 1% of viewport height
1vmin = 1vw or 1vh, whichever is smaller
1vmax = 1vw or 1vh, whichever is larger
h1 {
font-size: 5.9vw;
}
h2 {
font-size: 3.0vh;
}
p {
font-size: 2vmin;
}