$root-font-size: 16px;
@function rem($size) {
@return $size / $root-font-size * 1rem;
}
html {
font-size: ($root-font-size / 16px) * 100%;
}
.some-block {
font-size: rem(24px);
}
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="viewport" content="width=1024, initial-scale=1">