html{font-size: 62.5%; }div{font-size:2rem;} span {font-size:2em;}とした時
remとemについて(remはhtml基準、emは親要素基準)
https://jsbin.com/gekehumuca/edit?html,css
https://output.jsbin.com/gekehumuca
ブラウザの文字サイズ設定中の時＝16pxの0.625==>10px基準で、1.6remとすると16px扱い
https://i.gyazo.com/f5dd4b0233b5da1ba74ffb7788e78f01.png
https://i.gyazo.com/235eb45538351c3c828007004a2fbbc7.png
https://i.gyazo.com/5e62762a52a6bfa36955137790a19d27.png
html{font-size: 1vw; }div{font-size:2rem;} span {font-size:2em;}とした時
https://jsbin.com/gimipuduzu/edit?html,css
https://output.jsbin.com/gimipuduzu
https://i.gyazo.com/8e2504230224691e68e28392363a87a6.png
https://i.gyazo.com/c50510ffbb5c1925e31feecc536a532e.png
https://i.gyazo.com/945b0aeaf0e9edf33d3743cedd43fe24.png
https://i.gyazo.com/6a660a94fd9819adee757d7a3196bd4f.png
https://i.gyazo.com/7f68c33497d80e676de8b7da89485c9e.png
https://i.gyazo.com/5a0151055dd49e2c6348d3264edf4635.png
https://i.gyazo.com/a5b79467b5baf9732eff845fbb2d0347.png
https://i.gyazo.com/19d238d112d7133ebd8173ae8f30f66d.png
font-size: calc(10 / 375 * 100vw);div{font-size:2rem;} span {font-size:2em;}とした時
https://jsbin.com/huhekurido/edit?html,css,output
https://output.jsbin.com/huhekurido
https://i.gyazo.com/9be93436f9054428b6f65dbaeae1e19d.png
https://i.gyazo.com/fc743eeebf5e76d67a5ae303d2944cb3.png
https://i.gyazo.com/94e126747fbab4447b61bb134fb7273c.png
https://i.gyazo.com/9f836f3f2b7906efed8e251f8dbe780b.png
https://i.gyazo.com/d5ff68e8808a112f9c885d2d5a478be0.png
https://i.gyazo.com/a83b216e0da4fcae07e35b99d462c1cf.png