font size

Calculate font size through cacl
html {
    /* The 375px size of iPhone6 ​​is used as the 16px base, and the 600px size is exactly 18px*/
    font-size: calc(100% + 2 * (100vw - 375px) / 225);
}
@media screen and (min-width: 600px) {
    html {
        /* 600px-1000px increase 1px for every 100px wide font (18px-22px) */
        font-size: calc(112.5% + 4 * (100vw - 600px) / 400);
    }
}
@media screen and (min-width: 1000px) {
    html {
        /* 1000px is 0.5px for every 100px afterward*/
        font-size: calc(137.5% + 5 * (100vw - 1000px) / 1000);
    }
}


html {
    font-size: 16px;
}

Compatible with safari
@media screen and (min-width: 375px) {
    html {
        /* iPhone6's 375px size is used as 16px base, 414px is exactly 18px size, 600 20px */
        font-size: calc(100% + 2 * (100vw - 375px) / 39);
        font-size: calc(16px + 2 * (100vw - 375px) / 39);
    }
}
@media screen and (min-width: 414px) {
    html {
        /* 414px-1000px increase 1px for every 100px wide font (18px-22px) */
        font-size: calc(112.5% + 4 * (100vw - 414px) / 586);
        font-size: calc(18px + 4 * (100vw - 414px) / 586);
    }
}
@media screen and (min-width: 600px) {
    html {
        /* 600px-1000px increase 1px for every 100px wide font (20px-24px) */
        font-size: calc(125% + 4 * (100vw - 600px) / 400);
        font-size: calc(20px + 4 * (100vw - 600px) / 400);
    }
}
@media screen and (min-width: 1000px) {
    html {
        /* 1000px is 0.5px for every 100px afterward*/
        font-size: calc(137.5% + 6 * (100vw - 1000px) / 1000);
        font-size: calc(22px + 6 * (100vw - 1000px) / 1000);
    }
}