JSFiddle - React, Tailwind, and code Playground

HTML

<div class="floats overflow-hidden box-sizing">
    <div></div>
    <div></div>
    <div></div>
</div>

<div class="floats overflow-hidden known-width">
    <div></div>
    <div></div>
    <div></div>
</div>

<div class="floats overflow-hidden calc">
    <div></div>
    <div></div>
    <div></div>
</div>

<div class="floats after-pseudo">
    <div></div>
    <div></div>
    <div></div>
</div>

<div class="floats extra-markup">
    <div></div>
    <div></div>
    <div></div>
    <div class="clear"></div>
</div>

CSS

div.floats {
    padding: 10px;
    background-color: #eee;
    margin: 10px 0;
}

div.floats > div {
    float: left;
    width: 20px;
    height: 20px;
    background-color: #333;
}

div.floats > div + div {
    margin-left: 10px;
}

div.overflow-hidden {
    overflow: hidden;
}

div.box-sizing {
    width: 100%;
    box-sizing: border-box;
}

div.known-width {
    /* 200px - 2 * 10px of padding */
    width: 180px;
}

div.calc {
    width: calc(100% - 20px);
}

div.after-pseudo:after {
    content: "";
    display: block;
    clear: both;
}

div.clear {
    float: none !important;
    clear: both !important;
    width: 0 !important;
    height: 0 !important;
    margin: 0 !important;
}