How big is the largest whale?

The biggest whales are bigger than any land animal could be.
The largest blue whale accurately weighed by scientists to date was a female that weighed 177 metric tons (195 short tons), as much as 2,360 average men.
A whale can grow to such size because water holds up its weight evenly over its body, thus avoiding the concentrated forces at points of support that land animals must withstand. The whale's great size provides room for the muscles that give the whale swimming power. The entire rear third of a whale is an engine of enormous muscles. These enable the whale's 12-foot tail to move in a semicircular motion that works like a ship's propeller, building up as much as 520 horsepower in a 90-footer, according to the estimate of one scientist. Large blue whales can travel at 20 knots when necessary, and can run all day ahead of a whaling ship traveling at 10 knots.
All big whales except the sperm whale are baleen whales. They feed on small creatures of the sea by swimming along at slow speed with their mouths open. Their jaws are so wide that a tremendous amount of water pours in and is then forced out at the sides through the baleen strainers, which hang down like a curtain. Great numbers of tiny marine animals are caught in the baleen as the water passes through. Every now and then the whale's tongue wipes the baleen clean and passes the food back to its gullet.
Many whales pass about six months of the year in polar waters, where the feeding is best, and then travel to tropical seas to breed and bear young, undoubtedly so that their babies will have warm water to swim in until they grow a protective coat of blub­ber under their skin.