He's huge. Based on my footage, if Vordt stood up straight he'd be 5 or 6 times as tall as the player. Given similar proportions, mass scales with the cube of height, so that would make him 125 to 216 times as heavy. So assuming the player is an average-sized human (1.8 m tall and 75 kg) then Vordt would be 9 to 10 m tall and weigh 9400 to 16000 kg, not counting armor and gear. In terms of how much space he actually takes up in his dog-like posture, at a very rough estimate I'd say he's probably 3 m tall, 4 m long, and 4 m wide.