The largest animal on Earth based on weight is the blue whale (Balaenoptera musculus), which can weigh up to 160 tonnes (352,000 lb). Its average length is 24 m (80 ft), but it is not the longest animal on Earth. A huge specimen caught in the Southern Ocean, Antarctica, on 20 March 1947 weighed 190 tonnes (418,000 lb) and measured 27.6 m (90 ft 6 in).

Newborn calves are 6-8m (20-26 ft) long and weigh up to 3 tonnes (6,613 lb). The barely visible ovum of the female blue-whale weighing a fraction of a milligram grows to a weight of c. 26 tonnes (57,320 lb) in 22.75 months, made up of 10.75 months’ gestation and the first 12 months of life. This is equivalent to an increase of 3×10¹º.

Heaviest   A female weighing 190 tonnes (418,877 lb) and measuring 27.6 m (90 ft 6 in) in length was caught in the Southern Ocean on 20 March 1947.
Longest mammal   A female blue whale measuring 33.58 m (110 ft 28 in) landed in 1909 at Grytviken, South Georgia in the South Atlantic.

The longest known animal is the bootlace worm.