Sleep calculator / Chronotype
Chronotype Calculator
Night owl or early bird? Enter when you sleep on work days and on free days. It works out your chronotype from your sleep timing, plus how much "social jet lag" your schedule causes.
- 100% free
- No sign-up
- No app
Use times you actually fall asleep and wake up, not when you get into bed.
What is a chronotype?
Your chronotype is your body clock's natural timing: whether you tend to sleep and wake early (an "early bird" or lark), late (a "night owl"), or somewhere in between. In large surveys, people's natural sleep times spread out along a near-bell-shaped curve, with the most extreme early types waking up around when the most extreme late types fall asleep.
How the chronotype calculator works
It uses the approach developed for the Munich ChronoType Questionnaire, one of the most widely used research tools for chronotype:
- Mid-sleep on free days. The halfway point between falling asleep and waking up on days without an alarm. This is the core measure, because free-day sleep shows your body's own timing.
- Sleep-debt correction. If you sleep longer on free days to catch up, your free-day midpoint drifts later than your true chronotype. The calculator adjusts for that.
- Social jet lag. The gap between your mid-sleep on work days and free days. A big gap means your schedule is fighting your body clock, much like flying across time zones every weekend.
The early, intermediate and late labels are rough guides for comparison, not clinical categories. Your corrected mid-sleep time is the more useful number.
What to do with your result
- Night owl with an early start? Morning light and a consistent wake time, weekends included, are the most reliable ways to move your clock earlier. More on working with your chronotype.
- Big social jet lag? Keep free-day wake-ups within about an hour of work days. Is sleeping in on weekends bad?
- Find a bedtime that fits with the sleep calculator, or check how regular your sleep is.
Frequently asked questions
Can you change your chronotype?
Partly. Your chronotype has a built-in component, but light has a strong effect: more daylight, especially in the morning, and less bright light at night tend to move sleep timing earlier.
What is social jet lag?
The difference between the midpoint of your sleep on work days and on free days. Sleeping 11 PM to 6 AM on work days and 1 AM to 9 AM on weekends is about 2.5 hours of social jet lag.
Is being a night owl bad?
Not in itself. Problems tend to come from the mismatch between a late body clock and an early schedule, which can cause chronic sleep loss during the week.
Sources
- Roenneberg T, Wirz-Justice A, Merrow M. Life between clocks: daily temporal patterns of human chronotypes. Journal of Biological Rhythms, 2003.
- Roenneberg T et al. Epidemiology of the human circadian clock. Sleep Medicine Reviews, 2007.
- Wittmann M et al. Social jetlag: misalignment of biological and social time. Chronobiology International, 2006.
Related reading
- Is 7.5 Hours of Sleep Enough? Why 5 Full Cycles Often Feels Better Than 8For most adults, yes. 7.5 hours is inside the 7 to 9 hour range and equals exactly 5 sleep cycles. Who needs more, and bedtimes for 7.5 hours by wake time.5 min read
- How to Wake Up Refreshed: Cycle-Timed Alarms, Light and Enough SleepSleep at least 7 hours, set your alarm for the end of a sleep cycle, keep the same wake time and get light right away. Plus a cycle-timed alarm chart.4 min read
- How to Wake Up a Heavy Sleeper (Including Yourself)Time the alarm to the end of a sleep cycle, add light and a second alarm across the room, and fix short sleep. Plus when trouble waking is worth a doctor visit.4 min read
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- Daylight Saving Time Sleep PlannerA day-by-day plan to shift your sleep before the clocks change.
- Jet Lag CalculatorDays to adjust, plus a shift-before-you-fly schedule.
These results are general estimates, not medical advice. Everyone's sleep is a little different. If you're often exhausted despite enough time in bed, snore loudly, or have been told you stop breathing in your sleep, see a doctor.