I go by the width and color of the head markings... and it looks a bit narrower than most of my pullets. i'm leaning toward cockerel.usually I tell by the width and how well defined the stripe on the head is and how defined the eyeliner is. from what I see of yours, I think the eyeliner is pretty well defined, so maybe a girl?
to be sure, when the breast feathers come in they'll either be salmon (pullet) or black (cockerel) then you'll know for sure.