As the company’s sole owner, Blakely’s ingenious invention has made her rich.
Forbes currently estimates her net worth at $US1.01 billion.
Though she’s far less extravagant than other billionaires, she’s still making the most of her success.
Sara Blakely was born on February 27, 1971 in the beach town of Clearwater, Florida, and demonstrated an entrepreneurial instinct from an early age. At Halloween, she'd set up a haunted house, then charge her neighbours admission.
After graduating from Florida State University, she struggled to find a job and ended up working at Disney World. She thought about going to law school, but crashed and burned on the LSAT. The only job that she could find was selling fax machines.
That job ended up paying off, because it prompted her to invent Spanx. One night, she couldn't find the right hosiery to wear under white pants, so she decided to invent her own. Her first 'office' was her Atlanta apartment.
After fighting to get Spanx into department stores, Blakely worried that they'd drop the product if there weren't many buyers. So she called up everyone she knew and asked them to purchase Spanx, then mailed them a reimbursement check.
She kept her day job for two years while working to get Spanx into stores on the side, and only quit once Oprah named Spanx as one of her 'favourite things' in 2000.
Blakely's celebrity grew when she appeared on Richard Branson's TV show, The Rebel Billionaire, in 2004. The two have remained close and often swap business advice.
Today, Spanx is a billion-dollar business and Blakely remains the sole owner. She has never formally advertised or taken outside investments.
Blakely believes in facing her fears. Even though she's afraid of public speaking, she travels constantly to give speeches. And her fear of flying hasn't prevented her from jetting around the country for work. 'I took a Fear of Flying class, and I always missed the class, because I was always flying,' she told the New Yorker.
In 2008, she married Jesse Itzler, the cofounder of Marquis Jet, in Boca Grande, Florida. Olivia Newton John performed, and Matt Damon and his wife Luciana attended.
Before the wedding, Blakely had a moment of panic when she confessed a secret that she'd only told her immediate family: how rich she really was. Itzler had been under the impression that Spanx was making millions of dollars a year. The truth was that the number was in the hundreds of millions.
Today, their relationship is not exactly typical: over dinner with friends, Itzler found out that Blakely had put their La Jolla, California, house on the market and forgotten to tell him. 'I trust her to do whatever she wants,' he told Marie Claire.
Since Itzler's business is based in New York and Spanx is based in Atlanta, the couple's complicated lifestyle is made easier with a team of assistants, drivers, nannies, and chefs. Their son, Lazer, is 6.
But in many ways, Blakely is a typical mum: she drives a white Toyota minivan that her employees tease her about, volunteers at her son's school, and meets up with friends for margaritas after work.
Blakely keeps a lower profile than other billionaires, but has spent some of her hard-earned money on real estate. In 2011, she bought an $8.8 million beachfront home in Clearwater, Florida, where she grew up.
Blakely and her husband also bought a $12.11 million apartment at 15 Central Park West in 2008, then sold it for $30 million in 2014. Her fear of heights made living on the 37th floor difficult. According to Michael Gross, who wrote the book 'House of Outrageous Fortune' about the building, Blakely hired a Navy SEAL to design emergency escape routes from the building.
Blakely makes Atlanta her home base. Her 10,000 square foot solar-powered home there has a giant gumball machine in the foyer, and spa-quality steam and sauna rooms for her husband.
More than anything else, Blakely believes in giving back. She created a program called 'Leg Up' designed to help other female entrepreneurs grow their business. Participants get one-on-one mentoring with her, as well as free advertising in the Spanx catalogue.
She also founded the Sara Blakely Foundation in 2006, with the goal of contributing to causes that support women. In 2013, she signed The Giving Pledge along with Warren Buffett and Bill Gates, promising to donate at least half of her wealth to charity.
'I feel like money makes you more of who you already are,' she told Forbes in 2012, after making the billionaire list for the first time. 'If you're an arsehole, you become a bigger arsehole. If you're nice, you become nicer. Money is fun to make, fun to spend and fun to give away.'
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