Is Mauna Kea taller than Mount Everest?

Partly. Measured from sea level, Mount Everest is the highest mountain. Measured from base to peak, Mauna Kea in Hawaii is taller: about 10,200 m (33,500 ft), most of it underwater, versus Everest's 8,849 m above sea level.

What's actually true

Measured from base to peak, Mauna Kea is taller than Everest. Mauna Kea in Hawaii rises about 4,200 m (13,800 ft) above sea level, but most of the volcano is hidden underwater, reaching down about 6,000 m to the ocean floor. Measured from its base it is about 10,200 m (33,500 ft) tall, well over Mount Everest's 8,849 m above sea level.

Takeaway: "Tallest mountain" depends on whether you measure from sea level or the base.

Why people believe it

Both claims are true, which is why the argument never ends. 'Tallest' usually means 'highest summit above sea level', and by that measure Everest wins. Mauna Kea's base sits about 6,000 m below the Pacific surface, so most of the volcano is hidden. Because nobody sees an underwater mountainside, the base-to-peak comparison feels like a trick, but it is simply a different and equally valid way of measuring height.

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