You’re about to start, and you want one number for the timer. Maybe you’ve heard 90 minutes, or two to four hours, and wonder which is right. Or an hour already feels too long for you.
Here you’ll find out how long deep work sessions should be on a normal day. You also see when to go longer or shorter, and what to do when the timer rings.
Why 45 minutes is the default
On a day when you feel fit, focused and motivated, set the timer for 45 minutes. That’s the ideal length for one block, a timed stretch of focused work on one task.
This length uses your brain’s full capacity without making you very tired. My book builds the whole process around a 45-minute block.
The timer also tells your brain that the work has an end. That makes it easier to start, especially on unpleasant tasks. Without a timer, you either work too short or too long.
And the timer makes sure you take breaks, so you can do more focused work over the whole day.
So where do 90 minutes fit?
Is 90 minutes the best length for deep work?
Not for every block. Ninety minutes is for days of maximum fitness and motivation. On a normal good day, 45 minutes fits better than 60 or 90.
The psychologists Ericsson, Krampe and Tesch-Römer (Psychological Review, 1993) studied how violinists practice. For one week, the players kept a practice diary. Their sessions lasted 80 minutes on average.
The authors write that uninterrupted solo practice was limited to between 1 and 1.5 hours. Expert pianists in a second study practiced about 88 minutes per session, which the authors call a likely overestimate. That’s practice by musicians, not knowledge work.
The sessions of the best violinists were no longer than those of the other players. The study doesn’t test the best length for your work. So treat 90 minutes as a timer setting for your best days, not as a goal.
How long should you set the timer today?
On your best days and on all other days, set the timer to fit how you feel right now. So check how you feel right before each block.
Your deep work session length follows that check, not a fixed rule. Here are the five lengths to pick from.
| Length | Pick it when |
|---|---|
| 90 minutes | You feel at maximum fitness and motivation |
| 45 minutes | You’re fit, focused and motivated: the ideal |
| 35 minutes | You’re not fully fit, and 45 feels too long |
| 25 minutes | You feel unfocused today |
| 15 minutes | You’re strongly unmotivated; it helps you start |
If you’re unsure, set a shorter time, because you can always keep going when the timer rings. Even 15 minutes is better than skipping the block. Read about the minimum time for deep work.
The check is one honest question: am I awake, and can I think clearly? If you’re massively tired, no length fits: take a power nap of 10 to 20 minutes or postpone the block. For days like that, read how to focus when tired.
Is a deep work block 2–4 hours?
No: even on your best day, my book’s longest timer setting is 90 minutes. A block can run longer when you’re in flow, the state where you’re fully absorbed in the work. Two to four hours is a stretch of work made of several blocks, with a break after each one.
Each block gets its own timer and its own goal. The blocks don’t all have to be the same length. Your energy changes during the day: you might set 45 minutes in the morning and only 25 in the afternoon.
The four hours you may have heard of are a daily figure. The best violinists in the 1993 study practiced alone 3.5 hours a day. They spread that total over several sessions.
The same paper cites training studies that found essentially no benefit beyond four hours of practice a day. That limit is for a whole day, and it says nothing about one session. Read more about the evidence for four hours a day.
It’s better to plan one block too few than one too many. For the number of blocks, read how many deep work sessions you can do in a day. For the total, see how many hours of deep work per day.
What should you do when the timer rings?
When the timer of a block rings, check whether the work is flowing, then keep going or stop. The timer sets a length, and flow can overrule it. A block exists to get something done.
If you keep checking how much time is left, the work isn’t flowing. For the signs that a block is done, see when to stop a deep work session.
- In flow: turn off the timer and keep going until your brain needs a break.
- Not in flow: stop now and don’t add “just a bit longer.” Your brain needs the break, even if you don’t feel it.
- In both cases: take a real break, and make it longer after a longer block.
After 45 minutes of work, the break is 15 minutes, and after 90 minutes it’s 20 to 30. Set a timer for the break too. For the other lengths, read how long deep work breaks should be.
Then look at your block goal, the result you wrote down for this block. Note whether you reached it fully, partly or not at all, without judging yourself. Over time, this check shows you what fits into one block.
If you get stuck before the timer rings, don’t end the block. Find the next mini step, the next small thing you can do. Write it on your protocol sheet, the page with your block goal, then do it.
Mini steps, the goal check and a real break turn one good block into the next. That’s how a morning of two to four focused hours comes together. See how it works →
FAQ
What does Cal Newport recommend for deep work session length?
Cal Newport, author of Deep Work, advises students to study 50 minutes, then take a 10-minute break. His 2016 post “On Deep Breaks” says that few people stay at peak focus beyond about an hour without rest. The post sets no length for other deep work.
How long should a deep work session go without a break?
A deep work session should run without a break until it ends. Go to the bathroom before you start, so you don’t interrupt your work. If a distracting thought comes up, note it on a thought sheet, a page for such notes, and keep working.
Does the type of task change how long a deep work session should be?
How you feel today sets the length of a deep work session, and the task can shift it. I give creative work longer focus blocks so my flow isn’t cut off, but routine work gets shorter ones. Do demanding tasks when your energy is high.
Does writing your goal count toward a deep work session?
Writing your goal counts toward a deep work session, because the timer is already running. You set the timer, then write down your block goal, the result you want from this block of focused work. After that, you start working, with no more rituals.
