How time in bed and sleep efficiency are worked out
The hours you spend in bed and the hours you spend asleep are two different numbers. This calculator takes your bedtime and wake time to get time in bed, then subtracts the time it took to fall asleep and the time you spent awake during the night to get actual sleep time. If you woke more than once, it also shows the average length of an awakening.
Sleep efficiency is actual sleep time divided by time in bed, times 100, so the measure is arithmetic by definition. When the wake time falls earlier than the bedtime, the night is treated as crossing midnight and 24 hours are added. If the total time awake is not shorter than the time in bed, the calculation cannot stand and the page says so instead.
This page produces no sleep score or grade, and it names no percentage above which sleep counts as good, because that cut-off is not confirmed in an authoritative source. There is no way to know your sleep minutes exactly, so the result moves with whatever you remember. Current as of October 2026, and not a medical diagnosis. If low efficiency persists, or if there is snoring, witnessed pauses in breathing or heavy daytime sleepiness, see a clinician.
Frequently Asked Questions
This page does not name that cut-off. A widely quoted figure exists but it is not confirmed in an authoritative source, and a single night swings with whatever happened that day. Logging several nights the same way tells you more than one number does.
When the wake time is earlier than the bedtime, the page treats the night as crossing midnight and adds 24 hours. Lying down at 11:30 PM and getting up at 7:00 AM gives 7 h 30 min in bed.
Enter your best recollection. The page simply adds and subtracts what you type, so an estimated input gives an estimated output. Do not treat the result as a measurement.