<!doctype html>
<style>
#a {
background-color: #f00;
height: 50px;
width: 100px;
}
#b {
display: inline-block;
height: 100%;
}
svg {
background-color: #0f0;
height: 100%;
}
</style>
<div id="a">
<div id="b">
<svg viewBox="0 0 100 50">