Time in bed is everything from lights-out to getting up. Time asleep is only the part you actually spend sleeping. The gap between them is the time it takes to fall asleep, plus any time you lie awake in the night or in the morning. For most healthy adults, the gap is somewhere around 30 minutes to an hour.
That's why 8 hours in bed usually means closer to 7 or 7.5 hours of sleep, and why recommendations like "7 to 9 hours" refer to sleep, not time under the covers.
Free toolSleep Efficiency CalculatorWhat share of your time in bed you actually spend asleep.The pieces of a night
Sleep researchers break a night into a few parts:
| Term | What it means |
|---|---|
| Time in bed | From trying to sleep until you get up for the day |
| Sleep onset latency | How long it takes to fall asleep |
| Wake after sleep onset | Time awake during the night, after first falling asleep |
| Early waking | Time awake in bed after your final wake-up, before you get up |
| Total sleep time | What's left: the time you're actually asleep |
So: time in bed = time to fall asleep + total sleep + time awake in the night + time awake before getting up.
Most people underestimate the first and third parts. Brief wake-ups of a minute or two are normal and often forgotten, but longer stretches add up.
How to work out your own gap
You don't need a tracker. Estimate these for a typical night:
- What time did you get into bed to sleep? (Not the time you got into bed to scroll.)
- Roughly how long did it take to fall asleep?
- How long were you awake during the night, in total?
- What time did you wake for good, and what time did you get up?
Subtract the awake time from the time in bed and you have your total sleep. Divide total sleep by time in bed and you have your sleep efficiency. The sleep efficiency calculator does it for you.
Examples
| Time in bed | Time asleep | Time awake | Sleep efficiency |
|---|---|---|---|
| 7 h 30 min | 7 h | 30 min | 93.3% |
| 8 h | 7 h 30 min | 30 min | 93.8% |
| 8 h | 7 h | 1 h | 87.5% |
| 8 h 30 min | 6 h 30 min | 2 h | 76.5% |
| 9 h | 7 h | 2 h | 77.8% |
| 10 h | 7 h | 3 h | 70.0% |
Notice the last three rows. Spending more time in bed didn't buy more sleep. It mostly bought more time lying awake.
What's a normal gap?
Sleep clinicians commonly use about 85% sleep efficiency or higher as a sign of healthy, consolidated sleep. On an 8-hour night, that's roughly 6 hours 48 minutes asleep or more, with about 72 minutes or less awake.
Efficiency tends to fall with age. A large analysis of sleep-lab studies found that sleep efficiency keeps decreasing into later life, even in healthy people. So a slightly lower number in your 70s isn't automatically a problem.
At the other end, falling asleep the moment your head hits the pillow every night, with almost no time awake, can be a sign you're short on sleep rather than a sign of perfect sleep. Taking around 10 to 20 minutes to drift off is typical. More in how long does it take to fall asleep.
One catch: what counts as "in bed"
Researchers themselves don't fully agree on the denominator. One paper in the Journal of Clinical Sleep Medicine pointed out that time in bed, taken literally, includes reading, texting or watching TV in bed before you try to sleep. That makes efficiency look worse than it really is.
The authors proposed measuring from when you start trying to sleep to when you stop trying, and counting time out of bed during night-time wake-ups too. For your own estimate, that's the sensible approach: start the clock at lights-out, not when you climb in with your phone.
Why the gap matters
A big, regular gap between time in bed and time asleep is more than a curiosity:
- It hides how little you're sleeping. You may think you're getting 8 hours when it's really 6.5.
- It can reinforce poor sleep. Lots of time lying awake can train your brain to link the bed with being awake. See is it bad to lie in bed awake.
- It's what insomnia treatment targets. Cognitive behavioral therapy for insomnia works partly by closing this gap. Sleep restriction therapy explains how.
If your efficiency stays below about 85% for weeks, or you're tired during the day despite plenty of time in bed, it's worth talking to a doctor.