About the Chronotype Calculator
This chronotype calculator estimates your natural body-clock type from when you actually sleep. Enter your usual bedtime and wake time on work days and on free days (when no alarm wakes you), and it calculates your mid-sleep point corrected for catch-up sleep, your average sleep duration and your "social jet lag" — the gap between your body clock and your schedule.
The core measure is the one used by sleep scientists in the Munich ChronoType Questionnaire (MCTQ): mid-sleep on free days, corrected for the extra sleep people take to repay a work-week sleep debt (MSFsc). Earlier mid-sleep means a morning type; later means an evening type. The result is then expressed with the popular animal labels — lion for early birds, bear for the middle majority, wolf for night owls, and dolphin for light or restless sleepers — so it is easy to remember and share.
The animal names come from popular sleep books rather than clinical research, and the cut-offs used here (mid-sleep before 3:30 for lions, 5:30 or later for wolves) are this tool’s convention based on typical adult MCTQ distributions. Chronotype shifts later in the teens and earlier with age. If you have persistent insomnia or daytime sleepiness, talk to a doctor — a questionnaire cannot diagnose a sleep disorder.
How to use the chronotype calculator
- 1Enter when you usually go to bed and wake up on work or school days.
- 2Enter the same for free days when you wake without an alarm.
- 3Set how many work days you have per week and how long it takes you to fall asleep.
- 4Tick the light-sleeper box if you often wake in the night or rarely feel rested.
- 5Read your chronotype, corrected mid-sleep time and social jet lag.
Formula and method
Sleep onset is the time you fall asleep (bedtime plus the minutes it takes to drift off). Sleep duration (SD) runs from onset to wake time on work days (SDw) and free days (SDf). Mid-sleep is the halfway point. Because most people sleep longer on free days to repay a work-week deficit, the MCTQ corrects free-day mid-sleep by half of the extra sleep above the weekly average, giving MSFsc — the standard estimate of chronotype.
Social jet lag is the absolute difference between mid-sleep on free days and on work days. This tool labels MSFsc before 03:30 as lion, 03:30–05:29 as bear and 05:30 or later as wolf; ticking the light-sleeper box assigns dolphin regardless of timing.
- SDw, SDf
- Sleep duration on work days and free days
- MSW, MSF
- Mid-sleep on work days and free days
- WD, FD
- Number of work days and free days per week
- MSFsc
- Mid-sleep on free days, sleep-corrected (chronotype)
Worked examples
In bed 23:00 / up 6:30 on work days, 00:30 / 8:30 on weekends
With 15 minutes to fall asleep, work-day sleep runs 23:15–6:30 (7.25 h, mid-sleep 2:52) and free-day sleep 00:45–8:30 (7.75 h, mid-sleep 4:37). The weekly average is 7.39 h, so MSFsc = 4:37 − (7.75 − 7.39) ÷ 2 h ≈ 4:27 — a bear. The 1.75-hour gap between mid-sleeps is the social jet lag.
Night owl forced up early (sleep times entered directly)
Work-night sleep is only 6.25 h (mid-sleep 3:37) while free-day sleep is 8.5 h (mid-sleep 6:45). The weekly average is 6.89 h, so MSFsc = 6:45 − (8.5 − 6.89) ÷ 2 h ≈ 5:57 — a wolf, with over 3 hours of social jet lag.
Early riser
Free-day sleep runs 21:45–5:30, so mid-sleep is about 1:38. Free days give only 0.18 h more than the weekly average of 7.57 h, so the correction is small and MSFsc ≈ 1:32 — well before 3:30, making this a lion.
Frequently asked questions
What are the four chronotypes?+
The popular system describes lions (early risers who peak in the morning), bears (the majority, whose rhythm follows daylight), wolves (night owls who peak in the evening) and dolphins (light, restless sleepers). Scientists usually describe chronotype as a continuous scale from early to late instead.
How do scientists measure chronotype?+
A common method is the Munich ChronoType Questionnaire, which uses the midpoint of sleep on free days corrected for catch-up sleep (MSFsc). Another is the Morningness–Eveningness Questionnaire, which asks about preferred times for activities.
What is social jet lag?+
Social jet lag is the difference between your mid-sleep time on free days and on work days. It reflects how far your schedule pulls you away from your body clock; larger values have been linked with poorer sleep, mood and metabolic health.
Can I change my chronotype?+
Your underlying tendency is partly genetic, but it can shift with consistent habits. Bright light in the morning, dim light in the evening and regular wake times — even on weekends — can move your body clock earlier by an hour or so.
Does chronotype change with age?+
Yes. Children tend to be early types, chronotype becomes progressively later through adolescence, peaking around age 20, and then gradually shifts earlier through adulthood and old age.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.