How much of a CEO's day actually goes to email? Harvard tracked 27 of them to find out

Everyone assumes the person running a company lives in their inbox. It’s one of those claims that gets repeated so often it stops sounding like something you’d need to check. Harvard Business School researchers actually checked it: they tracked 27 CEOs, 24 hours a day, in 15-minute increments, for 13 weeks straight — vacations included. The result is one of the only real, measured (not self-reported) datasets on how much of an executive’s time actually goes to email, and the number is both bigger than you’d hope and smaller than the myth.

What the researchers actually measured

This wasn’t a survey where CEOs guessed at their own habits after the fact — a notoriously unreliable way to measure time use. Porter and Nohria’s team logged 27 CEOs of large companies (averaging $13.1 billion in annual revenue) around the clock, in 15-minute blocks, for a full 13 weeks. That’s roughly 60,000 hours of real, observed activity, including weekends and vacation days, where the CEOs in the study still averaged about two and a half hours of work.

The headline pace: 62.5 hours a week, 9.7 hours on an average weekday, plus another four hours on a typical weekend day. Inside that time, when the CEOs were communicating with someone, 61% was face-to-face, 24% was electronic — the study’s term for email and similar written digital channels — and 15% was phone calls and physical correspondence.

24% doesn’t sound like much. It is.

Run the arithmetic loosely against a 62.5-hour week and 24% of communication time lands somewhere in the range of a full working day, every week, spent on email and similar channels — and that’s before counting the 15% spent on phone and written correspondence that often overlaps with the same inbox. Put differently: electronic communication was the CEOs’ second-largest channel of any kind, behind only physically being in a room with another person, and ahead of every phone call, letter, and voicemail combined.

The study’s own framing is blunt about it: the authors describe email as a “dangerous time sink” for leaders specifically because it’s so easy to let it expand to fill whatever time isn’t already claimed by a meeting — unlike a call or an in-person conversation, which has a natural start and stop, an inbox has no edge. It just keeps accepting more.

The number that actually explains why it’s expensive

The 24% figure gets attention, but the more telling number in the same study is the 28% the CEOs spent completely alone — the single largest category the researchers measured, ahead of any form of communication. That solo, uninterrupted time is exactly the kind of deep-thinking, strategy-level work a CEO exists to do, and it’s also exactly the kind of time an always-open inbox is best at quietly eating into. The real cost of email isn’t the hours it directly consumes — it’s what those hours would otherwise have been.

That’s the same mechanical trade-off top-performing sales reps solve with block scheduling: the problem isn’t the total volume of any one task, it’s letting a channel with no natural stopping point interrupt the channel that actually needs protected, unbroken time to be worth anything.

Does this generalize past a $13 billion company?

The honest caveat here is that 27 CEOs of companies this large aren’t a stand-in for every executive, and especially not for the founder of a smaller company. A CEO running a $13.1-billion-revenue business has layers of support most founders don’t: an executive assistant screening what reaches the inbox at all, a chief of staff triaging what’s genuinely urgent, sometimes an entire office built around protecting the calendar. Strip that support structure away, as it is at almost every early-stage company, and there’s a reasonable case that the share of a founder’s time going to unfiltered email is higher than 24%, not lower — the study is measuring people with the most institutional protection from exactly this problem, and even they lose close to a quarter of their communication time to it.

Is 24% high, low, or about what you’d expect?

Context helps here, because no other study measures exactly this. McKinsey Global Institute’s frequently cited research on knowledge workers generally puts email specifically at about 28% of an average workweek — roughly 11.2 hours — a similar order of magnitude to the CEO figure, though it’s measuring a different population with a different method (self-reported, not observed) and a narrower definition (email specifically, not all electronic communication). Adobe’s 2019 consumer survey, asking a broad US sample to self-estimate, landed on 5 hours 52 minutes a day combined across work and personal email — which sounds enormous until you notice it’s actually down from 7 hours 45 minutes in 2016, one of the more genuinely surprising findings in this space: contrary to the “email is only getting worse” narrative, self-reported time spent on it had been falling, at least through 2019.

What this means if you’re the one sending, not just receiving

Every one of these studies describes the recipient’s side of the equation — the executive drowning in messages. If you run outbound at any company, you are, quite literally, one of the senders adding to that pile in someone else’s day. That’s not a reason to stop sending; it’s a reason to take seriously how much a genuinely relevant, well-timed message is worth against a background of that much competing noise, and why a crowded inbox changes how a recipient triages what lands in it.

It’s also, if you’re the founder running your own outbound, the same problem hitting you from the other direction. Founders running their own sales motion are simultaneously sending cold email and drowning in the replies, notifications, and inbound noise that generates — and a scattered stack of tools, each with its own notifications, makes the 24% worse, not better, because none of them agree on what actually needs your attention right now.

Adobe’s own 2019 study, worth remembering, was titled “If You Think Email Is Dead, Think Again” — a direct response to years of predictions that Slack, chat apps, and social platforms would finally kill it off. They haven’t. Every channel that was supposed to replace email got added on top of it instead, which is part of why a CEO’s electronic-communication share sits where it does even after a decade of “email is dying” takes. The channel didn’t shrink to make room for the new ones; the new ones just became additional inboxes to check.

Where Norbelys cuts into that number specifically

The lever isn’t sending less email — it’s spending less of your own scarce communication time re-deriving what’s already been sorted. Every reply your campaigns generate lands in one place, a single unibox, instead of scattered across however many mailboxes you’re sending from. Replies get classified automatically — interested, not interested, out of office, bounce — so the fraction of your day that goes to triage is spent on the handful of messages that actually need a founder’s judgment, not on re-reading auto-replies to find them. What a founder actually checks each morning takes minutes, not an hour, precisely because the sorting already happened before you opened the dashboard.

If email is already the second-biggest claim on your week behind being in a room with people, the only lever worth pulling is making sure every minute of it is spent on a message that’s actually earned your attention. See how Norbelys’s unibox and analytics work on every plan, and start running outreach that doesn’t cost you the 28% you’re supposed to be spending alone.