position:absolute; top:50%; left:50%; transform:translate(-50%,-50%);
<div id="outer"> <div id="inner">Foo foo</div> </div> //css:, demo with border <style> #inner { display: table; margin: 0 auto; border: 1px solid black; } #outer { border: 1px solid red; width:100% } </style>
margin:auto