How Long Should a Focus Session Be? 25, 50 or 90 Minutes
There is no universal best focus session length. Here's how 25, 50 and 90-minute blocks differ, plus a one-week test to find the one that fits you.
The short answer: 50 minutes is the safest default
If you want one number to start with, use 50 minutes of work followed by a 10-minute break. It's long enough to get past the awkward warm-up phase where you're still opening files and remembering where you left off, but short enough that you won't dread starting.
From there, adjust in both directions. Shrink to 25 minutes when the task feels heavy or you're low on energy, and stretch toward 90 when you're deep in something that's actually flowing. Session length is a dial, not a setting you choose once.
The worst option is no structure at all — an open-ended "I'll work until I'm done" block. Without an endpoint, your brain has no reason to start now rather than in ten minutes.
25 minutes: the starting-friction fix
The classic Pomodoro length exists because 25 minutes is psychologically cheap. Almost nobody can argue that they don't have 25 minutes, which makes it the right length for tasks you've been avoiding — the email you don't want to write, the assignment you haven't opened yet.
The tradeoff is that 25 minutes rarely gets you into deep work. Research on task switching suggests it takes several minutes just to reload context after an interruption, so a short block can be half warm-up. For writing, coding, or problem-solving, you'll often hit the timer right as things start clicking.
Use 25-minute blocks tactically: to break inertia, to clear admin work, or on days when your attention is genuinely fried. Don't treat them as your default if your work rewards depth.
50 minutes: enough runway for real work
A 50-minute block gives you roughly 10 minutes of settling in and 40 minutes of actual output. That ratio is why it's the standard length for university lectures and therapy sessions — it's about as long as most people can hold sustained attention without an artificial push.
Two 50-minute blocks in a morning will out-produce four 25-minute ones for most cognitive work, because you're paying the context-loading cost half as often. It also means fewer decisions about what to do next, which conserves the energy you'd otherwise spend restarting.
In Locked In, this is where an ambient companion earns its place. A 50-minute stretch is long enough for your attention to drift around minute 30, and a gentle check-in at that point pulls you back without breaking the session.
90 minutes: for flow, not for every day
Ninety-minute blocks map roughly to the body's ultradian rhythm — the natural cycle of alertness that rises and falls through the day. When you're rested and working on something you genuinely have traction with, 90 minutes can produce the kind of session you remember for a week.
But they're expensive. A 90-minute block that goes badly is 90 minutes of grinding, and it's hard to schedule more than two in a day without your quality dropping. Treat them as a reward for a task that's already unblocked, not a tool for starting one.
A useful rule: never open a 90-minute session on something you haven't already begun. Do a 25-minute block first to break ground, then commit the long one.
A one-week test to find your number
Pick the same type of work each day — writing, studying, whatever your core task is. On Monday and Tuesday run 25-minute blocks, Wednesday and Thursday run 50, Friday run 90. Same time of day, same place, no other changes.
After each session, note two things in one line: how much you actually produced, and whether you wanted to stop early or keep going. The pattern usually shows up by Thursday. Most people find one length where they consistently finish thinking "I could have done a bit more" — that's your number.
Locked In's session history makes this easy to see after the fact, since your completed sessions and their lengths are already logged. You're not tracking anything extra; you're just reading what you already did.
Match the break to the block, not the clock
Break length matters as much as session length, and the mistake is usually making them too short to recover from and too vague to end. After 25 minutes, take five. After 50, take ten. After 90, take at least twenty and get outside if you can.
What you do in the break decides whether the next session works. Scrolling feeds your brain the same kind of stimulation as your screen work, so you come back no fresher than you left. Standing up, drinking water, and looking at something more than six metres away costs nothing and works.
Set an end for the break too. An untimed "quick break" after a good session is the most common way a productive morning quietly ends at 11am.
Try a few lengths with Locked In
Locked In lets you set any session length you want, pick a vibe that fits the work, and lock in with a companion who checks in along the way instead of just counting down silently. The full timer, streaks, and the lock-screen widget are free forever, and you don't need an account to start.
Run a 25 tomorrow morning and a 50 in the afternoon, and see which one you'd rather repeat. That's usually all it takes to find the length you'll actually stick with.