How to center a CSS Hexagon - css

Question

Not sure how to center this hexagon, setting margin: auto; doesn't effect the whole shape. Grateful if anyone could help, thanks in advance.
.hexagon {
position: absolute;
width: 300px;
height: 173.21px;
background-color: #fff;
}
.hexagon:before,
.hexagon:after {
content: "";
position: absolute;
margin-left: auto;
margin-right: auto;
border-left: 150px solid transparent;
border-right: 150px solid transparent;
}
.hexagon:before {
bottom: 100%;
border-bottom: 86.60px solid #fff;
position: absolute;
margin-left: auto;
margin-right: auto;
}
.hexagon:after {
position: absolute;
top: 100%;
width: 0;
border-top: 86.60px solid #fff;
}

Answer 1

margin:auto won't work if you have absolutely positioned divs so to center the hexagon, you have to add top:50%, left:50% and margin: -86.6px 0 0 -150px. The -86.6px is half the height of your hexagon and -150px is the half of the width. Also you have to make its parent position relative with a height of 100%.
HTML
<div class="hexagon"></div>
CSS
html,body{
background-color:#333;
height: 100%;
width: 100%;
position:relative;
}
.hexagon {
top: 50%;
left: 50%;
margin: -86.6px 0 0 -150px ;
}
Fiddle

Answer 2

If you just mean centering horizontally, you could do this: http://codepen.io/pageaffairs/pen/fxoHp
.hexagon {left: 0; right: 0; margin: auto;}

Answer 3

You can put it into another div which has margin:auto. see code here http://jsfiddle.net/oswxj9c5/
html:
<div class="parent">
<article>
<div class="hexagon">
</div>
</article>
</div>
css:
.parent {
position:relative;
background:blue;
width:900px;
height:500px;
margin:auto;
}
article {
margin:auto;
width:300px;
height:300px;
background:transparent;
}
.hexagon {
position: absolute;
width: 300px;
height: 173.21px;
background-color: red;
top:150px;
margin:auto;
}
.hexagon:before,
.hexagon:after {
content: "";
position: absolute;
margin-left: auto;
margin-right: auto;
border-left: 150px solid transparent;
border-right: 150px solid transparent;
}
.hexagon:before {
bottom: 100%;
border-bottom: 86.60px solid red;
position: absolute;
margin-left: auto;
margin-right: auto;
}
.hexagon:after {
position: absolute;
top: 100%;
width: 0;
border-top: 86.60px solid red;
}