Center text in circle with SVG

I'm trying to center text in a circle with SVG. The size of the text will be dynamic.

My code on Plunker:

<svg xmlns="http://www.w3.org/2000/svg"
     xmlns:xlink="http://www.w3.org/1999/xlink"
     xml:space="preserve"
     style="shape-rendering:geometricPrecision; text-rendering:geometricPrecision; image-rendering:optimizeQuality; fill-rule:evenodd; clip-rule:evenodd"
     viewBox="0 0 500 500">

  <g id="UrTavla">
      <circle style="fill:url(#toning);stroke:#010101;stroke-width:1.6871;stroke-miterlimit:10;" cx="250" cy="250" r="245">
      
      </circle>
      <text x="50%" y="50%" stroke="#51c5cf" stroke-width="2px" dy=".3em"> Look, I’m centered!Look, I’m centered! </text>
  </g>
</svg>

Add text-anchor="middle" to the text element.

Plunker

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" xml:space="preserve" style="shape-rendering:geometricPrecision; text-rendering:geometricPrecision; image-rendering:optimizeQuality; fill-rule:evenodd; clip-rule:evenodd"
viewBox="0 0 500 500">
  <g id="UrTavla">
    <circle style="fill:url(#toning);stroke:#010101;stroke-width:1.6871;stroke-miterlimit:10;" cx="250" cy="250" r="245">
    </circle>
    <text x="50%" y="50%" text-anchor="middle" stroke="#51c5cf" stroke-width="2px" dy=".3em">Look, I’m centered!Look, I’m centered!</text>
  </g>
</svg>