In a Reddit AMA Monday night, Tesla Motors and SpaceX CEO Elon Musk revealed he sleeps “almost exactly 6 hours on average.”
That’s slightly below the average amount of daily sleep recommended by the National Sleep Foundation, which recommends adults over 18 get 7-9 hours of sleep each night in order to maintain a healthy weight and mood, as well as improve one’s memory and athletic performance.
It’s surprising the 43-year-old entrepreneur even manages six hours of sleep, considering he splits most of his days between his ambitious aerospace and automotive companies; he is also chairman of the green energy service company Solar City, a major philanthropist, and sits on several advisory and engineering boards.
If you’re wondering how Musk can accomplish as much as he does on little sleep, there are plenty of known ways to function at optimal levels on just four hours of sleep. Business Insider even has a step-by-step guide (with charts!) to help gradually reduce your sleeping hours while also getting more out of your waking hours.