I am 200px wide
I am 10vw wide
I am 10em wide
.wrapper { font-size: 1em; } .px { width: 200px; } .vw { width: 10vw; } .em { width: 10em; }
<div class="wrapper"> <div class="box px">I am 200px wide</div> <div class="box vw">I am 10vw wide</div> <div class="box em">I am 10em wide</div> </div>