JSFiddle - React, Tailwind, and code Playground

HTML

<div class="prop"></div>

CSS

.prop{
    background-color:red;
    border:solid black 8px;
    width: 40%; /* менять тут */
    box-sizing: border-box;
    border-radius: 200px;
}
.prop:after{
    padding-top: 100%; /* relative to width! */
    content: "";
    display: block;
}