How many years it took the 23 richest people in the world to go from millionaire to billionaire

• The richest people in the world found success at various ages.
• Warren Buffett spent over 25 years as a millionaire before becoming a billionaire, while it took Mark Zuckerberg only one year to graduate to billionaire status.
• Tech appears to be the fastest wealth-building industry; the richest people in tech averaged five years as millionaires before becoming billionaires.

The richest people in the world met success and wealth at various stages in life.

Facebook cofounder Mark Zuckerberg became a billionaire wunderkind at just 23 years old, while Berkshire Hathaway founder Warren Buffett's long-game investing strategies finally cemented his billionaire status at 56 - about 26 years after he first joined the seven-figure club.

Buffett and Zuckerberg are now the third and fifth richest people on earth, respectively.

Betway, an online betting site, used Forbes 2018 Billionaire's List and Bloomberg's Billionaire Index to find out how long it took the richest people in the world to go from millionaire to billionaire. The blog looked at when each person first appeared on either list, and also gathered news reports and rankings to pinpoint their age at the time. When it wasn't possible to find an exact age, Betway Insider made an estimate based on the individual's first big success in business.

Tech appears to be the fastest wealth-building industry; the richest people in tech averaged five years as millionaires before becoming billionaires.

Below, how long it took the richest people in the world to go from millionaire to billionaire. The list excludes two people - Françoise Bettencourt-Meyers and Mukesh Ambani - who both inherited their billions, skipping the millionaire stage completely. All current net worth figures are from Forbes' real-time ranking as of April 4.