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Sleep restriction

How to keep a sleep diary: what to write down, and when

Five times, two estimates, one minute each morning. What to record, how to estimate without a clock, and the mistakes that make a diary useless.

4 min read

Last reviewed October 7, 2026

Seven rows of sleep bars, one per night, with short gaps marking time awake

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A sleep diary takes about a minute each morning, and it is the instrument every decision in CBT-I is made from. Five times and two estimates, written down while the night is fresh. Done well, it shows patterns that memory reliably gets wrong. Done badly, it is useless. Here is how to do it well.

For why it matters so much, see why the sleep diary is the part that actually does the work. This article is the practical version.

What to record

The standardized research version of a sleep diary - the Consensus Sleep Diary - was developed so that diaries across studies record the same things. The core of it is:

  1. What time you got into bed.
  2. What time you tried to go to sleep, if that was later - for example, if you read first.
  3. How long it took to fall asleep, roughly.
  4. How many times you woke during the night, and how long you were awake in total.
  5. What time you woke for the last time.
  6. What time you got out of bed.

Worth adding: any naps, caffeine and alcohol, any sleep medication taken, and a quick rating of how rested you feel. They often explain a bad night that otherwise looks random.

When to fill it in

Each morning, within an hour or so of getting up. Not during the night, which means looking at the clock. Not at the end of the week, by which point the nights have blurred together.

How to estimate without a clock

Rough is fine. The diary is designed for estimates, and the patterns that matter show up across a week even if individual nights are imprecise.

What you should not do is watch the clock during the night to make the diary more accurate. Clock-watching tends to increase arousal - the arithmetic of how many hours are left is reliably bad for sleep. Turn the clock away and estimate in the morning. More on the 2am clock.

What you get out of it

From a week or two of entries you can work out three numbers:

  • Time in bed - from getting into bed to getting out of it.
  • Total sleep time - time in bed, minus time taken to fall asleep, minus time awake in the night, minus time in bed after the final waking.
  • Sleep efficiency - total sleep time divided by time in bed. What a good number looks like.

Those numbers are what the sleep window is calculated from, and what tells you when to widen it.

Take the free assessment to see:

  • ✓Your Insomnia Severity Index (ISI) score
  • ✓A personalized 6-week CBT-I plan, built by a sleep physician
  • ✓How your sleep improves, night by night
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The mistakes that make a diary useless

Filling it in from memory days later

Memory of bad nights is unreliable, and it tends to be unreliable in one direction: worse than the night actually was.

Skipping the good nights

A diary with only bad nights in it will set your sleep window wrong.

Changing your habits during the baseline

The first week or two should show how you sleep now, not how you sleep while trying hard.

Treating it as a score

It is a tool for adjusting the program, not a grade. If filling it in is making you anxious, that is worth noticing - and it usually eases once the patterns start to improve.

Paper, spreadsheet, or app

Any format works if you fill it in every morning. A structured CBT-I program usually builds the diary in and does the arithmetic for you, which removes the most common errors. A sleep tracker is not the same thing: it estimates sleep from movement and heart rate rather than recording it, and is not what the method is built on. Sleep apps vs CBT-I apps.

The rest of this section covers what to do with the numbers.

Somnera is a self-guided education program built on CBT-I, founded and written by Dr. Camilo Ruiz, DO, FACOI, FAASM. It is not a diagnosis and does not replace care from your own clinician. The assessment is free and takes about two minutes.

Citations

  • Carney CE, et al. The Consensus Sleep Diary: standardizing prospective sleep self-monitoring. Sleep. 2012;35(2):287–302. doi:10.5665/sleep.1642
  • Spielman AJ, Saskin P, Thorpy MJ. Treatment of chronic insomnia by restriction of time in bed. Sleep. 1987;10(1):45–56.
  • Harvey AG. A cognitive model of insomnia. Behav Res Ther. 2002;40(8):869–893. doi:10.1016/s0005-7967(01)00061-4
  • Edinger JD, et al. Behavioral and psychological treatments for chronic insomnia disorder in adults: an American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med. 2021;17(2):255–262. doi:10.5664/jcsm.8986

Frequently asked questions

When you got into bed, roughly how long it took to fall asleep, how many times you woke and for how long in total, when you woke for the last time, and when you got out of bed. Naps, caffeine, alcohol and sleep medication are worth noting too.

Each morning, within an hour or so of getting up, while the night is still fresh. Not during the night, and not in a batch at the end of the week.

No. Rough estimates are what the diary is designed for. Watching the clock during the night tends to increase arousal and make sleep worse.

One to two weeks gives a usable baseline before starting CBT-I. During treatment, the diary is kept every day, because the sleep window is adjusted from it week by week.

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