JSFiddle - React, Tailwind, and code Playground

HTML

<div id="box">This is the box.</div>

CSS

#box {
    width: calc(100% - 20%);
    background-color: #f90;
    font-weight: bold;
    color: #fff;
    line-height: 2em;
    text-align: center;
    margin: auto;
}