Most people imagine a CEO like Mark Zuckerberg trapped in back-to-back meetings, his time micromanaged down to the minute. After all, that’s the stereotype of billionaires like Bill Gates or Elon Musk—leaders who schedule every waking moment.
But in a recent fireside chat with Stripe co-founder John Collison, Zuckerberg revealed that his approach to productivity is the opposite. Instead of cramming his calendar, he leaves it open—and his system reflects a principle embraced by some of the world’s top performers, from Google executives to Albert Einstein.
It’s known as the 80% rule.
Why Zuckerberg Avoids Endless Meetings
When Collison asked Zuckerberg how he ensures he’s focused on the most important work for Meta, Zuckerberg admitted he rarely keeps standing one-on-one meetings. He talks to team members often—but informally.
Instead, he deliberately leaves large portions of his day unscheduled.
“Stuff is pretty dynamic,” he explained. “I wake up and think, ‘Okay, these are the three things I really need to work on today.’ I want to make sure I have the time to actually do them.”
Packed days, he said, are draining. “If my whole day is scheduled and there’s something important I don’t get to because I’m sitting in meetings, I get frustrated and in a bad mood. Too many days like that in a row and I just explode.”
By keeping time free, Zuckerberg can move quickly when priorities shift, reflect on bigger issues, and avoid burnout.
The 80% Rule in Action
Google’s in-house productivity coach, Laura Mae Martin, has given Zuckerberg’s loose philosophy a more precise label: the 80% rule.
Her advice to executives is simple—book only 80% of your schedule, and leave 20% open. That slack allows space to absorb the unexpected and stay flexible.
“I always tell people: under-commit so you end up committing at the right level,” Martin explained on the HBR IdeaCast. “That 80% target is where you’re involved in the right amount of things.”
Why High Achievers Embrace Strategic Slack
Zuckerberg isn’t the only one who works this way. Einstein famously left long stretches of his day open for thinking. Steve Jobs was another leader known for protecting free time in his schedule.
Productivity experts back up the approach, too. More than 20 years ago, software engineer Tom DeMarco argued in his book Slack: Getting Past Burnout, Busywork, and the Myth of Total Efficiency that overloaded calendars actually reduce performance. Without buffer time, people can’t absorb inevitable surprises and end up accomplishing less.
Other writers, including sociologist Christine Carter and journalist Oliver Burkeman, also champion what Carter calls “strategic slacking.” As Burkeman puts it: “I don’t embark on each day as if on a tightrope walk, needing everything to go exactly right in order to make it through the plan.”
What Percentage of Your Day Is Booked?
Zuckerberg might not use the term “80% rule,” but his practice embodies it. Leaving meaningful blocks of time unscheduled makes leaders more effective and more resilient.
Framing the idea as a specific percentage makes it easier to follow. Instead of vaguely telling yourself to “leave some time open,” you have a clear benchmark: 20% of your calendar should be free.
If a CEO running a company as massive as Meta can carve out time for reflection and flexibility, chances are you can too. And the experts are clear—scheduling less might be the key to accomplishing more.