Earth's Tallest Mountain: Mauna Kea (From Base) vs. Everest (From Sea Level)

The "biggest" mountain depends on measurement:

• From Sea Level: Mount Everest (8,848 m / 29,029 ft) is highest.
• From Base on Ocean Floor: Mauna Kea (Hawaii) rises ~10,203 m (33,474 ft) from its base 6,000 m below sea level—making it the tallest mountain on Earth by this measure.
• From Base to Peak (Land): Mauna Kea is second to Everest.

Mauna Kea is a dormant volcano; its summit hosts world-class astronomical observatories.