JSFiddle - React, Tailwind, and code Playground

HTML

<h3>Test Border</h3>
<div class="underline"></div>

CSS

h3 {
  font-size: 26px;
  display: inline-block;
  max-width:90px;
  margin-right:10px;
}

.underline {
  display: inline-block;
  border-bottom: 1px solid #c6bcb6;
  width: calc(100% - 104px);
}