/* Return zero if stored volume is zero */
if (Scientific::equals([VFL:m3], 0)) return 0.0;
/* Return unit height if stored volume equals unit volume */
if (Scientific::equals([VFL:m3], [V:m3])) return [h:m]+[DC:m];
/* Initialize */
$d2 = [D:m]*[D:m];
$v = M_PI/4*$d2*[h:m];
/* Return analytical solution if fill height is within cylindrical section */
if ([VFL:m3] <= $v) {
  return 4*[VFL:m3]/(M_PI*$d2);
}
/* Solve by Newton's rule */
$x = [h:m]+[DC:m]/2;
while (TRUE) {
  $h = $x-[h:m];
  $y = $v+M_PI/3*$h*(3/4*$d2-$h*$h)-[VFL:m3];
  if (Scientific::equals($y, 0)) return $x;
  $x = $x-$y/(M_PI*($d2/4-$h*$h));
}

Calculates fill height by using Newton's method of successive approximations (Newton's rule).