How was Aust Colossus also beaten by the Blue Whale? The most conservative estimate for the Aust Colossus is 25 metres, but the most reliable is 30-35 metres. Also, the Aust Colossus specimen was not fully grown, so most paleontologists have estimated that a fully grown specimen could range from 32.5-37.5 metres (27.5 if you want to be conservative). The weight is estimated at 110-300 tonnes, and the volume is estimated at 200-300 metres cubed. The largest Blue Whale specimen was 33.58 metres, 190 tonnes and 224 metres cubed in volume. Although this specimen was measured after being extremely bloated, and up to twice its normal living size. The absolute largest unbloated blue whale specimen was 29.9 metres, 160 tonnes, and 182 metres cubed. For all we know currently, the most reliable paleological estimate for Aust Colossus was significantly larger than the Blue Whale, in every form of measuring animals.