Circular Ring 2 tracks your period using skin temperature, HRV, resting heart rate, sleep, and recovery data. It reads them 24/7 to predict your next period, estimate your fertile window, and show how hormonal shifts affect your sleep, energy, and recovery.
Order Circular Ring 2Most period trackers ask you to log a symptom, count 28 days, and hope for the best. But your cycle changes month to month with stress, travel, sleep, illness, and routine changes. Predictions built on averages miss what's actually happening in your body, which means missed fertile windows, surprise periods, and unexplained fatigue you blame on yourself instead of your hormones.
Circular Ring 2 reads your body's actual signals around the clock and updates predictions as your physiology shifts.
Apps predict from 28 day averages. Your real cycle moves with stress, sleep, and travel.
Symptoms only get tracked when you log them. Let's be honest… Do you remember doing that?
Without temperature data, fertile window predictions are estimates and not data-backed.
Circular Ring 2 tracks your body's signals around the clock to detect where you are in your cycle and what's coming next. Period prediction stops being a calendar guess, fertile window estimation gets grounded in actual physiology, and your cycle connects to your sleep, recovery, and energy so you understand why your week feels the way it feels.
Continuous temperature monitoring, day and night, for accurate phase detection.
Circular combines temperature shifts AND resting heart rate to estimate ovulation and fertile windows.
Get notified ahead of your predicted period so you're not caught off guard.
Log symptoms and mood inside the Women's Health circle as they happen. Your notes help the system spot patterns over time, alongside the body signals the ring already tracks.
Identify your most fertile days based on body signals, not calendar math.
Switch modes and follow your pregnancy week by week, with body changes and weekly tips.
Your body's temperature trend shifts before your period arrives. Circular Ring 2 catches the pattern and gives you a heads up days in advance, so you can plan instead of react.
Whether you're planning ahead or simply learning more about your cycle, knowing your fertile days matters. Temperature and resting heart rate together estimate your fertile window based on what your body is doing this cycle, not last cycle's average.
Sleep gets restless. HRV drops. You assume something's wrong. Circular shows you it's a luteal phase pattern, and your body is doing what it's supposed to.
Energy and recovery shift across the cycle. Circular gives you the context so you can push when your body is ready and have some rest when your body needs it.
A late period after a stressful month or a bout of illness is normal, but only if you know what normal looks like for you. Circular tracks how your cycle adapts and recovers.
Temperature based fertile window estimation gives you a clearer picture of your most fertile days than calendar guessing ever could.
Kira watches your cycle data alongside every other signal Circular Ring 2 captures: sleep, stress, HRV, activity, energy, recovery, temperature and many other vitals. When your HRV dips mid luteal phase, Kira tells you it's hormonal, not a problem. When your sleep gets choppy before your period, Kira helps you protect your rest in advance. When your energy crashes mid cycle, Kira ties it back to where you are in your phase.
You know what is happening to and in your body, in plain language, and what to do about it.
The ring tracks your cycle using continuous body temperature, resting heart rate, HRV, sleep patterns, and your manual cycle input. These signals are read together to detect where you are in your cycle, predict what's coming next, and adapt to your individual pattern over time.
Menstrual, follicular, ovulation, and luteal phases are detected from the physiological shifts your body shows across the month, not from calendar math. Each phase comes with educational context inside the app so you know what's happening and why.
The system tracks the temperature trend shifts that happen before your period and updates your predicted date based on what your body is doing this cycle, not last cycle's average. You get a countdown of days before your predicted period and an alert before it arrives.
Fertile window estimation combines temperature shifts with resting heart rate to identify the days you're most likely to be fertile. You get a notification when your fertile window begins, with the system continuing to refine the estimate as your body responds across the cycle.
You can log how you're feeling (rad, good, normal, bad, awful) and track symptoms like headaches, hot flashes, mood changes, night sweats, breast tenderness, abdominal cramps, acne, and more. Manual logs work alongside the physiological data to give you a fuller picture of how your cycle moves your body and mind.
Switch into pregnancy mode and follow your pregnancy week by week, with information about how your baby is developing and how your body is changing. Cycle tracking pauses, and you get pregnancy specific symptom tracking and weekly tips delivered as you progress.
Your cycle phase is factored into how Circular Ring 2 interprets your sleep, recovery, energy, and stress. A drop in HRV mid luteal phase reads as a phase pattern instead of a problem, so your daily scores reflect what your body is actually doing.
Kira AI, your AI health coach, translates your cycle data into plain language. You get phase based suggestions throughout the month: prioritize recovery during your luteal phase, optimize sleep before menstruation, adjust activity load mid cycle, and watch for temperature deviations worth noting.
Temperature tracking runs around the clock, including during sleep, with no manual mode or button required. Predictions become more accurate after the first 2 to 3 cycles as the system learns your baseline.
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
Circular Ring 2 helps you understand the patterns behind your energy, sleep, recovery, and cycle so you can work with your body instead of against it.
"Not gonna lie, I downloaded Flo years ago and forgot to log stuff half the time. This is the first tracker that's actually worked with my real life instead of expecting me to remember everything."
"My periods aren't super regular, so calendar apps were always a bit off. The predictions with the ring have been way closer for me."
"Love that it explains WHY I suddenly have no energy instead of making me think I'm just lazy hahah"
Menstrual cycle tracking is one feature in a connected health system. Circular Ring 2 brings together sleep, stress, HRV, activity, SpO₂, temperature, energy, ECG, recovery, cycle, and pregnancy mode, paired with actionable AI insights from Kira AI. Your cycle data doesn't sit in a silo. It informs how your sleep is interpreted, how your energy is scored, and how your recovery is read.
All of it included. No subscriptions for the 14+ core features that matter.
Shows temperature changes from baseline. Variations beyond ±0.8°C (±1.4°F) may indicate significant health or environmental changes.
Overnight heart rate variability read against your own baseline, so you can see recovery move.
Light, deep and REM sleep mapped across the night, with the timing and quality of each stage.
Shows how much energy you've accumulated based on sleep, stress, recovery, and immune function.
Your complex data, turned into clear tips tailored to your lifestyle.
Your sleep, recovery, stress and activity combined into one daily score.
Both. Circular Ring 2 tracks your full menstrual cycle, predicts your period, estimates your fertile window, and identifies cycle phases based on your physiology. It also includes a pregnancy mode for users who want to track their pregnancy week by week.
Circular Ring 2 tracks your body temperature, resting heart rate, HRV, and sleep patterns 24/7. The system detects the physiological shifts that happen across your cycle, especially the temperature changes after ovulation, to estimate when your next period is likely to arrive. Predictions get more accurate after the first 2 to 3 cycles as the system learns your baseline.
Fertile window estimation uses temperature trends combined with resting heart rate to identify the days you're most likely to be fertile. Unlike calendar based predictions that assume a 28 day cycle, Circular Ring 2's estimation responds to what your body is actually doing this cycle.
Circular Ring 2 adapts to your individual cycle pattern, including variability month to month. Because predictions are based on physiological signals rather than calendar math, the system can adjust when your cycle runs longer or shorter than expected. Users with very irregular cycles, PCOS, or cycles affected by hormonal contraception may see different accuracy levels, and Circular Ring 2 continues to learn over time.
Yes. Many users wear Circular Ring 2 specifically to identify their fertile window when trying to conceive. The temperature based estimation gives you a clearer view of your most fertile days than calendar tracking alone. Circular Ring 2 supports reproductive health awareness, though it does not replace medical fertility consultation.
Yes. If you become pregnant, you can switch to pregnancy mode and follow your pregnancy week by week, with information about how your baby is developing and how your body is changing.
Your body temperature changes across your menstrual cycle. After ovulation, temperature rises slightly and stays elevated through the luteal phase. Tracking these shifts 24/7 lets Circular Ring 2 detect cycle phases based on what your body is doing, not what a calendar predicts.
No. Circular Ring 2 supports reproductive health awareness and helps you understand your cycle, but it does not diagnose conditions, confirm ovulation medically, or replace medical fertility tracking. If you have concerns about your cycle, fertility, or reproductive health, talk to a doctor.
No. Kira AI does not diagnose conditions, prescribe treatment, or replace medical professionals. It translates biometric signals into lifestyle and behavioral guidance you can act on. For anything clinical, the Circular app generates PDF reports and trend summaries designed to be shared with your doctor.
Yes. We encrypt data between your ring, the app, and our cloud systems. We do not sell your health data or use it for advertising, though we process and share limited data when needed to run, protect, and improve the service.
Circular Ring 2 is not intended to diagnose, treat, cure or prevent any disease, and is not for use in an emergency. It is not a method of contraception or birth control.
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