JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
  <div class="child">
    Bravo
  </div>
</div>

CSS

.parent {
   margin : 20px;
}
.child {
   width: calc(100vh - 40px);
   height : calc(100vh - 40px);
   margin:0 auto;
   background: red;
   box-sizing:border-box;
   padding:10px;
}