A free 90-minute focus timer with an automatic 20-minute break, built for deep work and long study blocks.
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It's one long, uninterrupted block of demanding work followed by a real break. This timer runs 90 minutes of focus and then starts a 20-minute break automatically. It suits deep work and long study sessions once you're comfortable concentrating for extended periods.
The number comes from sleep research. Nathaniel Kleitman, who co-discovered REM sleep, proposed a "basic rest–activity cycle" of about 90 minutes (often given as a range of 80 to 120), visible in the stages of sleep, and suggested that it continues through waking hours as swings in alertness. That idea is the source of most "ultradian rhythm" productivity advice.
The daytime part is the weak link. Some laboratory studies report fluctuations in alertness and performance on roughly 90 to 120 minute cycles; others, using stricter statistics, found no clear 90-minute rhythm. So treat 90 minutes as a practical upper limit for a block, not a biological law. The firmer evidence supports taking regular breaks, and nothing here shows that exactly 90 minutes beats 50 or 25. See our review of the Pomodoro research, and the 2025 controlled comparison in Flowtime vs Pomodoro, which found no clear winner between techniques.
| A good fit | Probably not yet |
|---|---|
| You can already concentrate for 50 minutes without strain | You find it hard to start or sustain attention (begin with 50/10 or 25/5 and build up) |
| The task needs long immersion: writing, research, design, difficult problem sets | Your day is full of interruptions you can't control |
| You can protect a long block on your calendar | The work is mostly short, reactive tasks |
If you have ADHD or attention difficulties, shorter blocks with visible structure are often easier; see our Pomodoro guide for ADHD.
Build up gradually: 25/5 first, then 50/10, then 90/20, over a few weeks. One or two 90-minute blocks a day is a realistic target for most people. For tools that support this way of working, see deep work apps and our focus techniques guide.
Part of it is. A roughly 90-minute cycle is well established in sleep stages. Whether the same cycle governs daytime alertness is contested: some studies find fluctuations on 90 to 120 minute cycles, others find no clear 90-minute rhythm. The evidence for taking regular breaks is stronger than the evidence for exactly 90 minutes.
There is no research-backed ideal. Fifteen to twenty minutes is a common choice, and this timer uses 20. Spend it moving, drinking water or resting your eyes rather than switching to another screen full of information.
For many people it is, at first. If you struggle to concentrate that long, start with 25 or 50 minutes and build up. Our 50/10 timer is a good stepping stone.
One or two is realistic for most people. Cal Newport has suggested that most people can sustain roughly one to four hours of truly deep work a day in total.
Yes, especially for demanding material. Mix long blocks with active recall rather than only re-reading; see productivity for students.
🇪🇸 En español: Temporizador de 90 minutos