JSFiddle - React, Tailwind, and code Playground

HTML

<div class="outer">
    <div class="inner"></div>
    <div class="inner"></div>
    <div class="inner"></div>
    <div class="inner"></div>
    <div class="inner"></div>
    <div class="inner"></div>
    <div class="inner"></div>
    <div class="inner"></div>
</div>

CSS

.outer {
    background-color: red;
    width: 200px;
    height: 200px;
    display: table-cell;
    vertical-align: middle;
}

.inner {
    box-sizing: border-box;
    border: 1px solid black;
    background-color: yellow;
    float: left;
}

JavaScript

var countDiv = $('.inner').length,
    outerWidth = $('.outer').css('width').replace('px', ''),
    singleWidth = outerWidth / countDiv + 'px';

$('.inner').css('width', singleWidth)
           .css('height', singleWidth);