function BDWcalc ()
  {
    var listeners = document.getElementById('listeners').value;
    var bitrate = document.getElementById('bitrate').value;
    var sati = document.getElementById('sati').value;
    var dana = document.getElementById('dana').value;
    var total = document.getElementById('BDWTotal');
    
    var sum = dana*sati*3600*bitrate/8*listeners/1024/1024;
    total.value = sum.toFixed(2)+" GB";
  }