This sleep calculator measures your actual sleep duration from bedtime to wake time, handling overnight spans.
Health
Sleep Calculator
Work backward from wake time, sleep cycles and fall-asleep time.
Calculator
About this calculator
Formula notes
duration = wake time − bedtime, wrapping past midnight; compare against the 7–9 h adult recommendation.
Worked examples
- Example: sleeping from 23:15 to 06:45 is 7.5 hours — within the recommended adult range.
- To wake at 07:00 after 8 hours of sleep, bedtime is 23:00; allowing 20 minutes to fall asleep moves the in-bed target to about 22:40.
How to use it
- Enter the time you went to bed.
- Enter the time you woke up.
- Read the total sleep duration.
Frequently asked questions
Does this count time awake in bed?
No. It measures the window only; sleep trackers are needed for actual asleep time.
Is 6 hours enough?
Most adults need 7–9 h; chronic 6 h sleep is linked to reduced performance and health risks.
Limits and interpretation
- Sleep cycles are not fixed 90-minute blocks, and counting cycles cannot guarantee waking in a particular stage.
- Sleep need varies by age and health; persistent insomnia, excessive sleepiness, snoring, or breathing pauses require clinical assessment.