Gold's market cap is the world's above-ground gold stock (about 216,000 metric tonnes, per the World Gold Council) multiplied by the current spot price per troy ounce. One metric tonne equals 32,150.7 troy ounces.
Above-ground tonnes × 32,150.7 troy ounces per tonne × spot price per ounce = total gold market capitalization in US dollars.
Gold is larger than any single public company and larger than the entire cryptocurrency market. It is the classic benchmark used in "Bitcoin vs gold" and "gold vs stocks" comparisons.
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