title: leaflet pixel size depending on zoom level
body: <p>I have to display 5x5 degrees pie chart on a leaflet map. I can display pie chart using the great <a href="https://github.com/humangeo/leaflet-dvf" rel="nofollow">leaflet-dvf</a> library, but I have to provide the radius in pixel, and it is static so far.</p>
  
  <p>I would like to have it dynamic so that at any zoom level, the pie chart fills the 5x5 square (aka radius = 5x5 degree length).</p>
  
  <p>How can I know the length in pixel of the side of a 5x5 degrees square, depending on the zoom level?</p>
  
  <p>Thanks</p>