Google maps latlng bounds with center and zoom level in map viewport

getBoundsAtLatLngWithZoom.js

function getBoundsAtLatLngWithZoom(map, center, zoom) {
  var p = map.getProjection();
  if (!p) {
    return null;
  }
  var el = $(map.getDiv());
  var zf = Math.pow(2, zoom) * 2;
  var dw = (el.width()  | 0) / zf;
  var dh = (el.height() | 0) / zf;
  var cpx = p.fromLatLngToPoint(center);
  return new google.maps.LatLngBounds(
    p.fromPointToLatLng(new google.maps.Point(cpx.x - dw, cpx.y + dh)),
    p.fromPointToLatLng(new google.maps.Point(cpx.x + dw, cpx.y - dh)));
}

Thanks for sharing! I spent a horrible amount of time trying to figure this out by myself :)