Mount Everest is not the world’s tallest mountain. Hawaii’s Mauna Kea is actually taller from base to summit, but it often doesn’t get the credit because over half of it is submerged below sea level.
And this is the view…
Oh, bless your precious, modern, college-educated hearts.
Depends entirely on how you define its “base”.
If you define it as “from mean sea level”, which is typically the baseline the world uses to measure altitudes, then Everest, at 29,028 ft. above mean sea level, is taller by 15,232 ft.
If you instead define it as “from the lowest point in the ocean”, the Mariana Trench at 36,070 feet beneath mean sea level (Everest: 65,098 ft., Mauna Kea: 49,866 ft.), then Everest is taller by 15,232 feet.
If you define it instead as “from the sea floor” then specify exactly which sea floor you’re referring to. Let’s use the arbitrary one specified in the infographic, 19,700 feet beneath sea level. Everest reaches 48,728 and Mauna Kea reaches 33,496 – Everest is still 15,232 feet taller.
See also: how to use a number line.