Circular Ring 2 tracks your sleep stages from light, deep, and REM sleep across the night, reads it alongside your recovery, stress, heart rate, and temperature, then turns every night into one specific, do-this-tonight recommendation.
Order Circular Ring 2Duration is the easiest thing to measure and the least useful thing to know.
The body moves through light, deep, and REM sleep across the night, and each stage does a different job. Miss one and you wake up as if you've been awake the whole night, no matter how long you spent in bed. Most wearables show you the chart and leave you to guess. Circular Ring 2 was built to do the opposite. Kira AI reads your sleep data, finds the pattern behind and turns it into one specific thing to change tonight.
Long sleep does not mean restorative sleep. You need more data about sleep stages.
Most apps hand you a sleep score, and never tell you what to change tonight.
The deeper analysis and actionable insights are usually held behind a monthly fee.
Circular Ring 2 tracks your full sleep architecture across the night, then reads it alongside every other signal (stress, heart rate, etc) your body sent in the last 24 hours. Kira AI then finds the patterns and gives you recommendations built on your personal patterns. Every morning, you wake up with your sleep data and a specific thing to adjust.
Light, deep, and REM sleep mapped across the night, with timing, duration, and quality of each stage.
One specific recommendation a day, tied to your sleep and the inputs that shaped it.
Stress, recovery, heart rate, temperature… You see what is actually affecting your nights.
Kira AI builds a 14-day rolling baseline of how your body sleeps, then flags shifts that fall outside it.
Wake up at the lightest moment of your sleep cycle and get your Wake Up Score, showing how ready your body is for the day.
Full sleep tracking, stage detection, and Kira AI's actionable insights are included with your ring.
See How Circular Compares
| Feature | Circular Ring 2 | Apple Watch 10 | Whoop 4.0 |
|---|---|---|---|
| Light, deep, REM stage tracking | Yes | Yes | Yes |
| Free actionable AI sleep insights | Yes | No | No |
| Multi-signal sleep correlation | Yes | Limited | Yes |
| 14-day personal baseline | Yes | Yes | Yes |
| Stress and recovery linked to sleep | Yes | Separate | Yes |
| Temperature trends in sleep view | Yes | Yes | Yes |
| Smart alarm aligned to sleep stages | Yes | No | Yes |
| Subscription free | Yes | Yes | No |
| Battery life | Up to 8 days | 18 hours | 4–5 days |
| Comfortable for overnight wear | Yes | Bulky for most | Bulkier |
You slept 8 hours but feel flat. Kira AI shows you spent most of the night in light sleep, with almost no deep sleep, and traces it back to a late workout. Recommendation: end intense training at least three hours before bed tonight.
Your REM sleep has been dropping for four nights running. Kira AI ties it to elevated stress scores in the late evening. Recommendation: a 3-minute coherence session before bed, at the time of day your stress tends to peak.
You woke up frequently and your temperature ran higher than your baseline. Kira AI connects it to a late dinner you logged in your notes. Recommendation: shift your last meal one hour earlier tonight.
Sleep onset is longer, REM is fragmented, your schedule is off. Kira AI ties it to the trip you logged and gives you a specific three-day plan to realign your circadian rhythm.
Your sleep duration is fine, but your bedtimes are scattered across a four-hour window. Kira AI surfaces the pattern and recommends a 30-minute anchor window to land in tonight.
Resting heart rate climbs overnight, temperature drifts up, respiratory rate shifts. Kira AI flags the change from your baseline. Recommendation: prioritize rest tonight, skip tomorrow's hard session.
Instead of waking mid-deep-sleep to a fixed alarm, you wake up at the lightest point of your last cycle, inside the window you set. Most users report waking up better, feeling refreshed and more productive within the first week.
A sleep stage chart on its own answers one question: how did I sleep. Kira AI answers the next one: what should I do about it.
Kira AI reads your sleep data alongside the rest of your last 24 hours. A short REM phase is not just a number. It is a pattern Kira AI ties back to your stress, your training load, your dinner timing, your temperature trend, the notes you logged about travel or alcohol. Every morning, the result is one actionable recommendation, written in plain language, built on the life and rhythm you live.
This is the difference between tracking sleep and improving sleep. A tracker shows you the chart. Kira AI tells you the action.
Circular Ring 2 tracks light sleep, deep sleep, REM sleep, and awake time. This shows the architecture underneath your sleep hours, so you can see how your night was actually built.
Total Sleep shows how long you slept overall. Real Sleep shows how much of your time in bed was actually sleep, also known as sleep efficiency. This helps you see the difference between time in bed and real rest.
Disturbances show the number of times you surface during the night, even if you do not remember them. These moments can cut your sleep into pieces while the total hours still look fine.
Tranquility shows how calm or restless your night was. A calm night and a restless night can last the same number of hours and feel very different.
Circular Ring 2 tracks sleep onset latency, which means the gap between lights out and real sleep. This helps you see whether your night started smoothly or took longer than usual.
Circular Ring 2 tracks whether your sleep timing is in sync with your body clock. Sleeping against your rhythm can affect how rested you feel, even when the hours look fine.
Sleep Debt shows what your body is still carrying forward from previous nights. One good night does not always erase a rough week.
Circular Ring 2 tracks what your heart does while your body is at rest. It adds another layer to your sleep and recovery picture.
Sleep tracking starts automatically when the ring detects sleep. There is no manual mode or button required. The ring is made for overnight wear, with a titanium body, 2.55 mm thickness, 7.8 mm width, and 3 gram weight.
Kira AI builds a 14 day rolling baseline from your sleep patterns. Your recommendations are based on your own data, not population averages.
Smart Alarm wakes you at the lightest moment of your final sleep cycle, inside a window you set. This is designed to reduce the heavy feeling that can come from waking during deep sleep.
Circular Ring 2 does not diagnose sleep disorders such as insomnia, sleep apnea, or restless leg syndrome. It does not replace clinical sleep testing. For any medical concern, share your sleep trends with your doctor.
Sleep data is encrypted and processed with GDPR and HIPAA compliance.
Titanium body, hypoallergenic interior
2.55mm thick, 7.8mm wide, 3 grams
Sizes: US 6–14
Battery: 8 days (Power Mode), 5 days (Performance)
Charging: 30 mins via wireless charger
ECG, PPG, temp sensor, 3x accelerometer
Bluetooth Low Energy, Airplane Mode
iOS & Android compatible
GDPR & HIPAA compliant
"I was sleeping 8.5 hours every night and still felt wrecked. Kira showed that my deep sleep was consistently low and connected it to late evening workouts. I moved training earlier and within a week I was waking up noticeably more refreshed."
"Perimenopause had me waking up at 3am for months. My old tracker told me how long I slept, but Circular showed what was happening inside that sleep."
"I didn't expect the ring to call out my late-night snacking, but here we are. The data kept showing worse sleep and lower recovery on the nights I ate close to bed, and Kira explained it in a way that actually made sense."
Sleep cycle tracking is one of 14+ core subscription-free health features built into Circular Ring 2. Sleep data does not sit in a silo. It feeds your Recovery Score, your Wake Up Score, your Energy Score, and Kira AI's daily recommendations. Stress, HRV, temperature, breathing patterns, activity load, ECG readings, and Women's Health signals all read together. That is what makes the actionable insights actually actionable.
Learn when your body is stressed and needs rest or when it is ready to perform
Shows temperature changes from baseline. Variations beyond ±0.8°C (±1.4°F) may indicate significant health or environmental changes.
Early warnings when metrics detect something unusual before you notice.
A 40-second ECG from your finger, with irregular rhythm and AFib detection.
Overnight heart rate variability read against your own baseline, so you can see recovery move.
Shows how much energy you've accumulated based on sleep, stress, recovery, and immune function.
Circular Ring 2 tracks sleep using a combination of accelerometer data, heart rate, heart rate variability, and skin temperature. These signals are read together to map your sleep across light, deep, and REM stages, as well as time awake.
Circular Ring 2 detects four sleep states: light sleep, deep sleep, REM sleep, and awake. It also captures sleep onset latency, total sleep duration, sleep efficiency, and number of awakenings during the night.
Most sleep trackers show you stages and a score. Circular Ring 2 reads sleep alongside stress, recovery, heart rate, temperature, and activity load, then Kira AI turns the full picture into one actionable recommendation a day, built on your personal 14-day baseline. The core sleep tracking and the insight layer are included with the ring, not held behind a subscription.
No. Full sleep tracking, sleep stage detection, smart alarm, and Kira AI's actionable insights are included with Circular Ring 2 at no additional cost. There is no monthly fee.
Sleep duration is only one part of recovery. The body needs adequate deep and REM sleep to wake up rested. Circular Ring 2 shows you the architecture of your night so you can see whether the time was actually restorative, and Kira AI surfaces what is interfering with the stages you need most.
Circular Ring 2 uses multiple signals together to classify sleep stages, including motion, heart rate, HRV, and temperature. For accuracy to be reliable, the ring needs a stable fit, overnight wear, and a baseline of at least 14 days to calibrate to your personal patterns.
Sleep tracking is built for overnight sleep. A daytime nap may be picked up depending on how long it lasts and how clear the signal is, but naps are not scored the way a full night is.
No. Circular Ring 2 does not diagnose sleep disorders such as insomnia, sleep apnea, or restless leg syndrome. It is not a substitute for polysomnography or clinical sleep evaluation. For clinical concerns, share your trend data with your doctor.
Yes. The smart alarm wakes you at the lightest moment of your final sleep cycle, inside a window you set. The goal is to wake you when your body is naturally closest to consciousness, rather than mid-deep-sleep.
Kira AI reads your sleep architecture alongside your stress, recovery, heart rate, temperature, activity, and manual notes from the same 24-hour window. It then generates one actionable recommendation each morning, written in plain language, calibrated to your personal baseline.
Yes. Sleep architecture, duration, and consistency are core inputs into both your Recovery Score and your Energy Score. A night of poor REM or fragmented deep sleep will be reflected in both scores the following day.
Often, yes. Elevated stress, especially in the late evening, can delay sleep onset, shorten REM sleep, and increase nighttime awakenings. Kira AI tracks this connection across days so you can see how your stress patterns are shaping your nights.
Kira AI uses a 14-day rolling baseline. After the first two weeks of overnight wear, insights become reliable, and they continue to refine the longer you wear the ring.
The ring is 2.55mm thick, 7.8mm wide, and weighs 3 grams. Most users forget they are wearing it. There is no screen, no vibration, and no light, so it does not interrupt sleep.
Circular Ring 2 is not intended to diagnose, treat, cure or prevent any disease, and is not for use in an emergency.
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