Tim Cook has joined the billionaire club, as Apple's valuation continues to rise.

The chief executive now has a net worth of more than $1 billion, according to calculations by the Bloomberg Billionaires Index.

His rising fortunes are largely aligned with the growth of the company he runs. A 5 per cent share price increase last week helped push Mr Cook's net worth over the threshold, and he has overseen a huge rise in the value of Apple.

The company was worth a relatively small $350 million when founder Steve Jobs died, leaving Mr Cook in permanent control of the company. It is now worth almost $2 trillion, as it like other large tech companies grows during the coronavirus pandemic.

Bloomberg calculated Mr Cook's estimated net worth by looking at regulatory filings and working out how his various investments are likely to have appreciated over time, it said.

It noted that Mr Cook could have less money if he has made undisclosed charitable donations. He said in 2015 that he was planning to give most of his wealth away, and that he had already made a series of gifts of the Apple shares that he owns.

Much of Mr Cook's wealth comes from his ownership of Apple shares, which have been given to him throughout his career. He now owns almost 850,000 of the company's shares, or 0.02 per cent, which together are worth $375 million.

He has accrued shares in the company since 1998, when he joined Apple and worked in its operations and supply chain. He was given a huge set of restricted shares when he became chief executive nine years ago, and has received further payouts since.

The rest of Bloomberg's calculations are made up from previous sales of shares, dividends from that stock and other compensation from Apple, which adds the remaining $650 million.

Mr Cook is still ranked relatively low among his fellow billionaires. His estimated net worth is not enough to get him into the top 500 of Bloomberg's Billionaires Index, and other chief executives such as Jeff Bezos and Bill Gates are at the top with comfortably more than $100 billion.

He is also unusual among his fellow, more wealthy chief executives – such as Facebook's Mark Zuckerberg, Amazon's Jeff Bezos and Tesla and SpaceX's Elon Musk – in that he did not found his company and does not own a large stake in his own company. Apple shares are by contrast more widely distributed, and as a result it has not created one standout billionaire among its employees in the same way.

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