You could just do this with stroke-dasharray
:
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100">
<circle cx="50" cy="50" r="30" stroke-dasharray="0.628" stroke-width="2"
fill="none" stroke="black"/>
</svg>
Example: http://jsfiddle.net/75WsM/