Free tool
Sleep efficiency calculator
Sleep efficiency is the share of your time in bed that you spent asleep. Enter a night below to see the figure. Nothing you type is saved or sent anywhere.
Night 1
Fill in a night to see the figure.
What this figure means
Sleep efficiency is time asleep divided by time in bed. In the behavioural method (CBT-I), people keep a diary and look at this figure as an average over a week. It is one input to how time in bed is set. It is not a measure of how healthy your sleep is, and one night on its own says very little.
Educational, not a diagnosis.
If you are worried about your sleep, or you snore loudly, stop breathing at night or feel very sleepy in the day, we suggest you speak to a clinician.
Learn more
What sleep efficiency is
Sleep efficiency compares two numbers. The first is how long you spent in bed, from getting in to getting out. The second is how long you were asleep in that time.
Divide time asleep by time in bed and you get a share. If you spent 8 hours in bed and slept for 6 of them, the share is three quarters.
The method uses this share because it is easy to work out from a paper or web diary. It does not need a watch or a ring.
How to keep a sleep diary
Fill in the diary each morning, for the night just gone. Write down when you got into bed, roughly how long it took to fall asleep, and how long you were awake in the night.
Then note when you woke for the day and when you got out of bed. Your best guess is fine. Do not check the clock in the night to get it exact, as that can keep you awake.
If you want a paper copy, there is a free printable diary with the same boxes.
Why one night tells you little
Sleep changes a lot from night to night. A late meal, a noisy street or a busy day can move the figure a long way.
That is why the method looks at an average over at least seven nights. A week of entries shows a pattern that one night cannot.
This calculator takes up to seven nights and shows the average once you add a second night.
How this calculator handles midnight and clock changes
Most people go to bed before midnight and get up after it. The calculator moves morning times to the next day, so 23:30 to 07:00 counts as 7 hours 30 minutes.
It also uses real elapsed time. On the night the clocks go forward, the night is an hour shorter, and the sum reflects that. This is the same maths the course diary uses.
Questions
Common questions
- How do you work out sleep efficiency?
- Divide the time you spent asleep by the time you spent in bed. Time asleep is the time from getting into bed to waking for the day, minus the minutes it took to fall asleep and the minutes you were awake in the night.
- Does a higher figure mean my sleep is healthy?
- No. Sleep efficiency is a piece of diary arithmetic. It does not measure how healthy your sleep is, and this tool does not assess your sleep. If you are worried, speak to a clinician.
- Why does the calculator ask for the date?
- On the two nights a year when the clocks change, the night is an hour longer or shorter. Knowing the date lets the calculator count the real time you spent in bed.
- Is anything I enter saved?
- No. The sum runs in your browser. Nothing you type is stored or sent to us.
- Can I use a sleep tracker instead of a diary?
- The method uses a diary, not a wearable. Trackers estimate sleep in their own way, and their numbers do not always match what you remember. A diary records the night as you lived it.