For this you can use display:table-cell
property:
.inline {
display: inline-block;
margin: 1em;
}
.wrap {
display: table;
height: 100px;
width: 160px;
padding: 10px;
border: thin solid darkgray;
}
.wrap p {
display: table-cell;
vertical-align: middle;
}
<div class="inline">
<div class="wrap">
<p>Example of single line.</p>
</div>
</div>
<div class="inline">
<div class="wrap">
<p>To look best, text should really be centered inside.</p>
</div>
</div>
But it works IE8 & above. Read this article for more info: CSS Tricks: Vertically Center Multi-Lined Text.