Better Sleep DiaryFree tool
Sleep efficiency calculator
The share of your time in bed that you spent asleep. Enter last night, or your averages for a week.
- In bed
- 8h 5m
- Asleep
- 7h 15m
That's 85% or more, the level insomnia treatment usually aims for.
How it's worked out
Sleep efficiency is your total sleep time divided by your time in bed, times 100. Time in bed runs from when you go to bed until you get up. This is the definition in the American Academy of Sleep Medicine's insomnia guideline, and the one the Better Sleep Diary app uses.
If you choose Time awake, the calculator works out your sleep the way a sleep diary does: time in bed, minus the time it took to fall asleep, minus the time you were awake in the night, minus any time you lay awake before getting up.
An example: in bed from 22:45 to 06:50 is 8h 5m. Asleep for 7h 15m of that gives 90%.
What the number tells you
Low efficiency means a lot of time in bed awake: taking a long time to fall asleep, waking in the night, or waking early and staying in bed. It's one of the main numbers sleep clinics look at in an insomnia diary. In cognitive behavioural therapy for insomnia (CBT-I), 85% is the level usually used to decide whether to change the time allowed in bed.
One night says little. Work out your efficiency each morning for a week or two, and look at the average and at which nights were low.
This calculator isn't medical advice. Don't cut your time in bed to raise the number without a clinician: sleep restriction is a treatment that needs supervision. If poor sleep has gone on for months or makes the day hard to cope with, see your doctor.
Questions
What is a good sleep efficiency?
Insomnia treatment usually aims for 85% or more, and the app colours a night green from 85%. A lower figure on one night isn't a problem in itself; the pattern over a week or two tells you more.
Why is my efficiency low when I slept enough hours?
Efficiency compares sleep with time in bed, not with how much sleep you need. Seven hours asleep is 78% if you were in bed for nine.
Does the time to fall asleep count as time in bed?
Yes. Time in bed runs from going to bed until getting up, so lying awake at the start, during the night or before getting up all lowers your efficiency.
Is the result the same as in Better Sleep Diary?
Yes. The calculator uses the same rule as the app: time asleep divided by the time between bedtime and getting up, from 0% to 100%.
Can I enter a week of nights?
Enter your average bedtime, wake time and sleep for the week to get a weekly figure, or use the online sleep diary to work out each night and the average for you.
Sources
- Clinical Guideline for the Evaluation and Management of Chronic Insomnia in Adults. American Academy of Sleep Medicine, Journal of Clinical Sleep Medicine, 2008.A two-week sleep log before the first visit, what it records, and how total sleep time and sleep efficiency are worked out from it. Checked 7 November 2026.
- Measuring Sleep Efficiency: What Should the Denominator Be?. Journal of Clinical Sleep Medicine, 2016.Sleep efficiency is usually total sleep time divided by time in bed; insomnia treatment commonly uses 85% as its threshold. Checked 7 November 2026.
- Behavioral and psychological treatments for chronic insomnia disorder in adults. American Academy of Sleep Medicine, Journal of Clinical Sleep Medicine, 2021.CBT-I is the recommended treatment for chronic insomnia, and it is guided by sleep diaries kept through treatment. Checked 7 November 2026.