Sleep Duration Calculator

1. Enter your bedtime and wake-up time. Use the time you got into bed and the time you got up. Nights across midnight work automatically.
2. Estimate time to fall asleep and time awake. Add up every wake-up in the night. Rough estimates are fine.
3. Pick your age group. The result is compared with the recommended range for your age.

Sleep duration is the amount of time you are actually asleep, which is always less than the time you spend in bed. The gap is made up of the time it takes to fall asleep and any time you lie awake during the night.

That difference matters. Eight hours in bed can easily be under seven hours of sleep. Most adults need 7 to 9 hours of actual sleep, teens 8 to 10 and children aged 6 to 12 need 9 to 12.

Sleep efficiency describes the same gap as a percentage: the share of your time in bed that you spend asleep. For a week-long view of your nights, use the sleep statistics calculator.

The calculator measures your time in bed, subtracts the time spent awake, and compares the result with your time in bed and your age group.

1. Time in bed: 11:00 PM to 7:00 AM = 480 minutes (8 h).
2. Subtract 15 minutes to fall asleep and 20 minutes awake: 480 – 35 = 445 minutes.
3. Sleep time: 445 minutes = 7 h 25 min.
4. Efficiency: 445 / 480 = 93%.
5. Cycles: 445 / 90 = about 4.9 cycles.

Eight hours in bed became 7 h 25 min of sleep, which is inside the adult range. If the same person lay awake for an hour and took 30 minutes to fall asleep, sleep would drop to 6 h 30 min and efficiency to 81%.

Hours in bed between common bedtimes and wake times. Your actual sleep is shorter by the time it takes to fall asleep and any time awake. Open a cell for that night in detail.

For example, 11 PM to 6 AM is 7 hours in bed. With 15 minutes to fall asleep and 15 minutes awake, that is 6 h 30 min of sleep, below the adult minimum.

Choose My average sleep over a week in the calculator and enter the hours you slept each night. It adds them up and divides by the number of nights.

A week of 6.5, 6, 7, 6.5, 6, 8.5 and 9 hours averages 7 h 04 min. That sits inside the adult range, but four nights were under 7 hours: the long weekend nights hide a short working week.

Time To Fall Asleep

Stress, caffeine and screens late in the evening lengthen it. Every extra minute comes straight off your sleep.

Night Awakenings

Short wake-ups add up. Several five-minute wake-ups can cost half an hour.

Age

Sleep efficiency tends to fall with age: one population study found it dropped from about 85% in people aged 39 to 49 to about 76% in people over 80.

Time In Bed

Spending much longer in bed than you sleep lowers efficiency. Matching bedtime to your real sleep need usually helps.

If your sleep duration is short but efficiency is high, you probably need an earlier bedtime; the bedtime calculator helps. If efficiency is low, the issue is time awake in bed.

• Anyone who feels tired despite spending enough time in bed.
• People checking a sleep tracker against their own estimate.
• People with short nights who want to see how much sleep they are really missing; the sleep debt calculator adds that up over a week.

Counting Time In Bed As Sleep

This is the most common error and it hides short sleep.

Forgetting Night Wake-Ups

Brief awakenings are easy to forget but add up quickly.

Judging One Night

Sleep varies. Look at several nights before drawing conclusions.

Ignoring Low Efficiency

Regularly spending a lot of time awake in bed is worth discussing with a doctor, especially if it lasts for weeks.

The arithmetic is exact, but the result is only as accurate as your estimates of time to fall asleep and time awake.

Take the time from getting into bed to getting up, then subtract the time it took to fall asleep and any time awake in the night.

Add up the hours you slept each night and divide by the number of nights. Choose the week option in the calculator to do it for up to 14 nights.

10 PM to 6 AM is 8 hours in bed. With 15 minutes to fall asleep and 15 minutes awake in the night, that is 7.5 hours of sleep.

Sleep efficiency of 85% or higher is generally treated as normal. Below 85% means a large share of your time in bed was spent awake.

Divide the time you were asleep by the time you were in bed and multiply by 100. For example, 7 h 25 min asleep in 8 h in bed is 93%.

11 PM to 7 AM is 8 hours in bed. Your actual sleep is shorter once you subtract time falling asleep and time awake.

Trackers estimate sleep from movement and heart rate and may count quiet wakefulness as sleep. Your own estimate of time awake can differ.

Seven hours meets the minimum for most adults. The recommended range is 7 to 9 hours; teens and children need more.

Yes. Studies show it tends to fall with age as sleep becomes lighter and more broken.

Add the wake-ups together and enter the total. If broken sleep continues for weeks, talk to a doctor.

• Factors involved in sleep efficiency (PMC, population study) (definition; efficiency falls with age)
• Hypersomnia Foundation: Sleep efficiency (85% or higher is normal)
• Canadian Sleep Research Consortium: Sleep efficiency (below 85% on average is too low)
• MedlinePlus: Healthy sleep (sleep need by age)
• NHLBI: How much sleep is enough (sleep need; sleep debt)