Sleep Efficiency Calculator
Sleep efficiency calculator
Sleep efficiency = time asleep divided by time in bed. 85% and above is the normal range.
You fall asleep quickly and stay asleep. Nothing to fix here.
Track this for a week and average it. One bad night is noise. A week under 80% is the pattern worth taking to a doctor.
Sleep efficiency is the one sleep number that is both easy to measure at home and clinically meaningful. It answers a different question from every other calculator on this site: not when to sleep, but how much of the time you set aside for sleep you are actually using.
The formula
Sleep efficiency (%) = (total sleep time / total time in bed) × 100
Total time in bed runs from getting in to getting out, including the time you lay there reading or scrolling. Total sleep time is that figure minus sleep latency (how long it took to drop off) and minus wake after sleep onset, the minutes you spent awake in the middle of the night.
Reading your score
| Efficiency | Interpretation | What to do |
|---|---|---|
| Above 95% | Likely sleep-deprived | Extend time in bed by 15-30 min |
| 85-95% | Normal range | Nothing. Hold the schedule. |
| 75-85% | Below target | Trim time in bed, fix the wake time |
| Below 75% | Poor | Sleep restriction protocol; see a doctor if it persists |
Why the fix is less time in bed, not more
The instinct when you are sleeping badly is to go to bed earlier and give yourself more chances. It reliably makes things worse. Extra hours in bed get filled with wakefulness, and the brain learns the association: bed becomes the place where you lie awake and worry about being awake.
Sleep restriction reverses it. You compress time in bed to roughly the amount you are actually sleeping (never below 5 hours), keep the wake-up time fixed, and let sleep pressure do the work. Efficiency climbs, usually within a week or two. Once you are consistently above 90%, you add 15 minutes back. Then again. The schedule grows to fit the sleep instead of the other way round.
Expect the first few days to be unpleasant. That is the mechanism working, not a sign it is going wrong. If you drive, are pregnant, or have bipolar disorder or a seizure disorder, do this under clinical supervision rather than alone.
Measuring it honestly
- Estimate rather than clock-watch. Checking the time at 3 AM makes the number worse and the night longer.
- Fill in the diary in the morning, once, for the previous night.
- Average across seven nights. One night tells you nothing.
- Wearables systematically overestimate sleep, because lying still reads as sleep. Use them for trends, not for the raw efficiency figure.
Next: rebuild the schedule around a fixed wake-up time with the sleep schedule calculator, or check what your current times actually total with the hours of sleep calculator.