Every focus timer I've ever opened defaults to 25 minutes. Taskaro's Focus Mode does too, because it's the number everyone expects. But I've started sessions with that default open while working on something like a two-hour writing block, and the timer running out on minute 25 wasn't a helpful checkpoint. It was just noise that broke my concentration for no reason connected to the actual task.
That's the part nobody explains when they tell you to "set a 25-minute timer": the number was never chosen for you. Here's where it actually comes from, and how to pick a length that matches what you're doing instead of what an app assumes.
One clarification before the research: this post is about how long a single session should run. How many of them to run in a day is a different question with a different answer, and it's covered in how many Pomodoros you should actually do in a day.
Where 25 Minutes Actually Comes From
The number traces back to Francesco Cirillo, a university student in the late 1980s who grabbed a tomato-shaped kitchen timer (pomodoro is Italian for tomato) and set it to whatever it happened to be set to: 25 minutes. It wasn't derived from a study on attention span. It was the number already on the dial.
That doesn't make it a bad number. 25 minutes is short enough to commit to even when you don't feel like starting, which is most of what makes the Pomodoro method work in the first place. But there's no reason to treat it as a fixed law rather than a reasonable starting point that happened to stick.
The Case for Longer Sessions
Some sleep and productivity researchers have proposed that attention runs in cycles of roughly 90 minutes, alternating between higher and lower alertness across the day, an idea usually called ultradian rhythm. The theory isn't settled science with one number everyone agrees on, but the general shape of it matches what a lot of people notice anecdotally: a short warmup, a stretch of real focus, then a drop-off that no amount of willpower fixes.
If that's closer to how your attention actually behaves, a 25-minute timer doesn't protect your focus, it interrupts it right as you're getting into the work. This is especially true for tasks with real startup cost: writing, debugging, reading something dense. You lose the first several minutes just reloading context, and a 25-minute cutoff can mean you're stopped right as that cost finally paid off.
Match the Length to the Task, Not the Other Way Around
The more useful question isn't "how long should a focus session be." It's "what am I about to do." A few honest defaults:
- 25 minutes for shallow, well-defined tasks: clearing an inbox, reviewing a short PR, drafting a quick reply. Low startup cost, easy to finish inside the window.
- 50 minutes for medium tasks with some ramp-up: writing a section of something, working through a bug you've already found, planning a week.
- 90 minutes or longer for deep work with real startup cost: first drafts, unfamiliar code, anything where the first 10 minutes are just remembering where you left off.
None of these are rules either. They're a starting point for noticing which one actually fits, which only shows up after you've tried a task at more than one length.
Breaks Still Matter More at Longer Lengths
The tradeoff with longer sessions is that the break after them has to do more work. A 5-minute break after 25 minutes is enough to reset. A 5-minute break after 90 minutes usually isn't, and skipping a real break to keep working is exactly how a long focus session turns into a long stretch of declining output that just doesn't feel finished. If you're running 90-minute blocks, plan on breaks closer to 15 to 20 minutes, away from the screen.
How I Actually Set This in Focus Mode
Focus Mode ships with a 25-minute default chip because it's the safest assumption for a first session. But the custom duration option, up to 8 hours, exists specifically for this: pick a task from your board, and if it's the kind of thing that needs an hour and a half of uninterrupted time, set it to that instead of pretending it's a 25-minute task because that's the number the app suggested first.
The honest test is simple. If you keep finishing early or getting restless before the timer ends, the session is too long. If the timer interrupts you right as you're finally in it, it's too short. The Pomodoro method's real rules matter more than its default number, and the length is the part you're meant to adjust.
If the timer itself keeps failing, here's why that happens.
There's No Universal Right Answer
25 minutes works for a lot of people because it's low commitment and it's the default everyone's heard of. It's not a law of attention, just a kitchen timer's setting that stuck. Try a task at 25, then try the same kind of task at 50 or 90, and let what actually happens decide it, not the number the app opened with.