How many tons of gold have ever been mined?

How to get close to this number

Work from the cube. The explanation gives the comparison directly: all the gold ever mined would form a cube around twenty-two metres on each side. Gold is about nineteen times denser than water, so cube the side length, multiply by that density, and the tonnage falls out.

The cube is the fact worth keeping because it inverts the intuition entirely. A substance that has driven wars, funded empires and underpinned currencies for five thousand years fits comfortably inside a tennis court. Scarcity is the whole of gold's value, and the cube is what scarcity looks like when you stack it up.

Worth noting that almost all of it still exists. Gold does not corrode, is rarely consumed industrially in ways that destroy it, and is recycled relentlessly — so the total ever mined and the total in existence are nearly the same number. Very few commodities have that property, and it is why the cumulative figure is meaningful at all.