Circadian Rhythm Calculator: Find Your Body Clock
Your circadian rhythm is the roughly 24-hour internal clock that shapes when you feel alert and when you feel sleepy. A circadian rhythm calculator and a chronotype quiz help you see where your own clock sits so you can plan around it.
Key takeaways
- Your body clock runs on a cycle of about 24 hours and is set mainly by light.
- A chronotype describes whether you naturally lean towards mornings or evenings.
- Your mid-sleep time on free days is a simple way to estimate your chronotype.
- Aim to align your schedule with your clock where your life allows.
What is a circadian rhythm?
The circadian rhythm controls patterns such as sleepiness, body temperature and hormone release across the day. Morning light is the strongest cue for keeping it in step with the 24-hour day. Our circadian rhythm calculator turns your sleep and wake times into a simple summary.
Find your mid-sleep time
On days when you sleep without an alarm, note when you fall asleep and when you wake. The midpoint is your mid-sleep time. For example, sleeping from 1:00 AM to 9:00 AM gives a mid-sleep time of 5:00 AM. A later mid-sleep time suggests an evening type, and an earlier one suggests a morning type. Many adults fall somewhere around 3 to 5 AM.
Morning types, evening types and in-between
Researchers describe a spectrum from early types (“larks”) to late types (“owls”), with most people in the middle. Chronotype changes with age: teenagers tend to shift later, and older adults often shift earlier. Take the chronotype quiz and read chronotypes explained.
Planning around your clock
- Keep a regular wake-up time, even if your bedtime is late.
- Get morning light to nudge a late clock earlier.
- Schedule demanding work for when you feel most alert.
- Avoid bright light late at night.
Shift work and jet lag
Working against your clock can make sleep harder. See our guides on shift work and jet lag.
Frequently asked questions
Can I change my chronotype?
Light, routine and age can shift it a little, but it has a strong biological basis.
Is a late chronotype unhealthy?
Not by itself. Problems come from a mismatch with fixed early commitments.
Sources and further reading: American Academy of Sleep Medicine (aasm.org), Sleep Research Society, National Sleep Foundation (sleepfoundation.org), CDC sleep resources (cdc.gov/sleep). See our full source list and editorial policy. This guide is general information, not medical advice.