How big is a blue whale, really?

The short answer

A large adult blue whale is about 30 metres long - roughly 100 feet - and weighs up to around 120 tonnes according to NOAA. That length is about sixteen times the height of a typical adult human, and the mass is in the region of 25 to 30 adult elephants.

It is also the largest animal known to have ever lived. Not the largest living animal - the largest animal, full stop, exceeding any dinosaur for which we have good fossil evidence. The blue whale is bigger than the thing you are probably mentally comparing it to.

Why the comparison is harder than it looks

There is a conceptual problem with putting a blue whale on a height chart. The whale is long, not tall. Its total length is roughly 29-30 m, but its maximum vertical extent - the height of its body from belly to back - is on the order of 4 m in the thickest part.

So a comparison board that shows 29 m vertically is answering the question "how long is it relative to a person", not "how tall does it stand". That is a legitimate and useful comparison, but it is worth being explicit about, because it is the single most common source of confusion in whale size graphics. If the whale were drawn lying next to a person at true scale, the person would be smaller than the whale's eye.

The numbers behind the picture

Figures follow NOAA's published description of the species (up to about 100 feet and 120 tonnes). Heart and tongue figures circulate widely and derive from a small number of dissections, so treat them as good approximations rather than precise measurements.

Getting an intuitive grip on the scale

Thirty metres is hard to picture. These are the comparisons that actually help:

• A ten-storey building. At a typical 3 m per floor, a blue whale would reach roughly the height of a ten-storey block laid on its side.
• Sixteen people stacked head to foot. An 18 m queue of adults still falls short. This is the number that surprises people most - the whale is not "a few people long", it is more than a dozen.
• A bus and a half. A standard 12 m city bus is less than half the length of a large blue whale.

Why it got that big, and why nothing else did

Size in water is easier than size on land. Buoyancy removes the structural problem of supporting a body against gravity - the same issue that limits how large land animals can grow. A whale's skeleton does not have to hold its own weight, which removes the ceiling that constrains terrestrial animals.

The second factor is food. Blue whales are filter feeders, straining krill through baleen plates. Krill is abundant in cold, nutrient-rich water, and a filter-feeding strategy lets an animal of enormous size collect enough calories without needing to chase individual prey. The result is the largest animal in the history of life on Earth, living on organisms roughly the size of a human thumb.

Put it on the board

The comparison below shows a blue whale's length as a vertical extent next to a human, a giraffe and a T. rex. The whale compresses everything else, which is itself the point - remove it from the board and the land animals become legible again.