Musk made history as the world's first paper trillionaire earlier in June following the blockbuster float of his SpaceX rocket company.
Shares in the business soared after debuting on Wall Street, peaking at around $US200 ($A290) per share, which boosted Musk's personal wealth due to his 38 per cent stake in the business.
However, the share price has slumped by about 30 per cent since the peak and is now roughly on par with the opening price on the first day of trading.
In that time, Musk's fortune soared from an estimated $US1.1 trillion to $US1.45 trillion during the peak trading day, before falling back when the stock price sank, according to calculations by Forbes.
He is now worth an estimated $US962 billion, as of the end of trading on Tuesday, Forbes reported.
Furthermore, the share price of Tesla, Musk's electric car maker, has also been subject to swings this week, partly after getting swept up in a widespread sell-off of technology stocks in the US.
The massive movements in his personal fortune reflect the volatility of the trillionaire status, which is tied to company valuations rather than physical money.
He nevertheless remains the world's richest man, having also built his wealth from a stake in social media platform X, formerly Twitter.
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