JSFiddle - React, Tailwind, and code Playground

HTML

<div class="input-container">
    <input type="text" value="102.95" name="" />
    <span class="unit">Volts</span>
</div>
<div class="input-container">
    <input type="text" value="30" name="" />
    <span class="unit">Kilos</span>
</div>
<div class="input-container">
    <input type="text" value="64" name="" />
    <span class="unit">km/h</span>
</div>

CSS

.input-container {
   position: relative;
    width: 150px;
}
.input-container input {
    width: 100%;
}

.input-container .unit {
    position: absolute;
    display: block;
    top: 3px;
    right: -3px;
    background-color: grey;
    color: #ffffff;
    padding-left: 5px;
    width: 45px;
}