IE 11 ignores font-size - html

Question

In IE11 the font-size of my navigation bar is much much smaller than in other browsers.
In my CSS file, I set body { font-size:16px; } which I would like to make a default font-size for the document.
For all other elements I use em units.
I set font-size:1.5em for <a> in my navbar, which should be 24px, but IE11 ignores that and the font-size is only 16px. Same thing happens to some other text on the website (h1, h2, span).
When I inspect the element I see that IE11 shows 1.5em size as the one that is assign to it, but the result of calculation is only 16px.
Other browsers (including Edge) displays the website properly.
* {
border: none;
margin: 0;
padding: 0;
text-decoration: none;
line-height: normal;
list-style-position: inside;
}
* {
-moz-box-sizing: border-box;
-webkit-box-sizing: border-box;
box-sizing: border-box;
}
body {
color: #666;
font-family: 'Roboto', Arial, Tahoma, sans-serif;
font-size: 16px;
font-weight: normal;
padding: 0;
margin: 0 auto;
background-color: #fff;
}
nav#top {
float: right;
display: inline-block;
}
nav#top ul {
list-style: none;
display: inline;
}
nav#top ul li {
list-style: none;
display: inline;
float: left;
}
nav#top ul li a {
display: block;
float: left;
padding: 30px 10px;
font-size: 1.5em;
font-family: 'Lato', sans-serif;
font-family: 'Arimo', sans-serif;
color: #fff;
text-shadow: 1px 1px 1px #060;
}
<nav id="top">
<ul class="clearfix">
<li>Label 1
</li>
<li>Label 1
</li>
<li>Label 1
</li>
<li>Label 1
</li>
<li>Label 1
</li>
</ul>
</nav>
I googled about font-size:100% !important and similar solution, but didn't find anything that works.

Answer 1

Please try this:
nav#top ul li a {
color: #fff;
display: block;
float: left;
font-family: "Arimo",sans-serif;
font-size: 24px;
padding: 30px 10px;
text-shadow: 1px 1px 1px #060;
}

Answer 2

This will not comply with every use case, but it's the way that has reduced my headaches dramatically.
To achieve an overall good cross browser experience, I would suggest that you in general remove font-sizes from the body tag and let the browsers do their magic.
Although - at first glance - it seems that you might loose control over the design, I have learned that you get more consistent results if you remove most of the font-size properties.