Circular Ring 2 helps you understand your fertile window using real body signals, not just calendar dates. It tracks your overnight temperature, resting heart rate, HRV, and cycle logs to estimate ovulation and period timing.
Order Circular Ring 2A 28-day cycle is an average, not a rule. Your cycle can change with stress, sleep, illness, travel, and routine. Circular learns your pattern over time, so your predictions are based on what your body is doing now.
Kira AI turns your data into one simple daily recommendation, so you know when to rest, log a symptom, protect your sleep, or prepare for the days ahead.
Many apps build predictions around a fixed cycle length, even when your body changes month to month.
Symptoms matter, but you do not feel or log every shift. Some of the most useful signals happen overnight.
A static prediction ignores stress, travel, illness, and the cycle-by-cycle variability that defines real bodies.
Circular Ring 2 tracks your cycle through body signals, not calendar math. It reads overnight temperature, resting heart rate, HRV, sleep, and your cycle logs to estimate your fertile window and period timing.
Your body temperature often rises after ovulation. Circular tracks these small changes overnight to help estimate where you are in your cycle.
Temperature is important, but it is stronger with context. Circular also looks at resting heart rate, HRV, sleep, and cycle logs.
Your predictions improve as Circular learns your cycle across several months. The longer you wear it, the more personal the pattern becomes.
Kira AI helps explain how your cycle may be affecting sleep, energy, stress, and recovery. You get one clear recommendation a day, written in simple language.
Ovulation tracking, fertile window estimates, period prediction, and Kira AI insights are included with Circular Ring 2's core features.
You decide to start trying for a baby. The app estimates your fertile window from your temperature shift, and each cycle makes the prediction more accurate because it learns from your body.
Your calendar predicted next Tuesday. Your temperature shifted on Friday, and the app updated your prediction. Your period arrived Sunday, matching your body's signals instead of a calendar estimate.
Poor sleep and lower HRV make you think something is wrong. The cycle view shows you're in your luteal phase, where these changes are common, helping you understand what your body is doing.
Your energy drops at the same point every cycle. Instead of guessing, you can show the pattern and plan around it together.
Travel disrupts your sleep, stress, and cycle. The system adapts to your body's changes and updates your period prediction accordingly.
After stopping hormonal contraception, your cycles feel unpredictable. Instead of assuming a 28-day cycle, the app adapts to your unique pattern as it develops.
A stressful month or a few rough weeks can shift your cycle. The ring shows the changes in temperature and HRV, and Kira AI puts them in context as your cycle settles back over the following weeks.
A fertile window estimate on its own is a date range. What is more useful is understanding how the rest of your body is responding across the cycle.
Kira AI reads your cycle alongside every signal Circular Ring 2 captures, including your sleep stages, HRV trend, stress, recovery, and temperature. When HRV drops in your luteal week, it explains it as a phase pattern, not a problem. When your sleep gets choppy before menstruation, it helps you protect your rest in advance. When you are approaching your fertile window, it surfaces the relevant context for the days ahead.
You get one clear thing to do each day. Built on your data, written in plain language.
The ring tracks ovulation and fertility window using continuous overnight body temperature, resting heart rate, heart rate variability, sleep patterns, and your manual cycle input. These signals are read together to detect phase transitions and refine predictions over time.
Body temperature rises after ovulation. Continuous overnight tracking picks up this subtle shift without a manual morning reading.
The fertile window is estimated by reading temperature shifts together with resting heart rate. Unlike calendar-based apps that assume a fixed 28-day cycle, Circular adapts the estimate to what your body is doing this cycle.
Period prediction tracks the temperature trend shifts that precede menstruation and updates the predicted date based on your current cycle, not last cycle's average. You get a notification ahead of your predicted period.
Menstrual, follicular, ovulation, and luteal phases are detected from the physiological shifts the ring tracks across the month. Each phase comes with educational context inside the app.
Predictions become more accurate after the first 2 to 3 cycles, as the system learns your individual baseline. The longer you wear the ring, the more refined the predictions become.
Circular Ring 2 is not a medical device and does not diagnose conditions, confirm ovulation, or predict fertility with clinical certainty. It is not a method of contraception. Accuracy may vary for users with PCOS, irregular cycles, perimenopause, or fertility concerns. Consult a healthcare professional if needed.
Inside the Women's Health circle, you can log how you feel and any symptoms as they happen. Your manual notes help the system detect patterns more accurately over time, alongside the physiological signals the ring is already tracking.
All cycle and reproductive health 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
"Got it mostly for cycle and ovulation tracking. I like that it uses my temperature and heart rate, not just the calendar. My cycle shifts a bit, so seeing the pattern in the app makes it easier to understand what is going on."
"Way easier than logging everything manually. I still add symptoms sometimes, but the ring picks up the sleep, temp and HRV changes on its own. The fertile window alerts have been helpful and the app is simple enough."
"Good fertility tracker so far. Took a couple cycles to feel more accurate, which makes sense. I like seeing how my sleep and energy change before my period too. Would love more detail in some cycle reports, but overall I'm happy."
Your cycle is not separate from the rest of your body. Sleep changes across phases. HRV shifts in the luteal week. Energy moves with hormonal patterns. Circular reads all of it as one system, with 14+ core features connected, including sleep, HRV, stress, recovery, ECG, heart rate, temperature, breathing, and coherence. The fertile window estimate gets sharper because none of it sits alone.
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.
Period predictions built from your temperature, heart rate and sleep, not a 28-day calendar.
Your complex data, turned into clear tips tailored to your lifestyle.
Every movement sorted into low, medium or high effort, with a daily calorie count beyond workouts.
Circular Ring 2 tracks your overnight temperature, resting heart rate, HRV, sleep, and cycle logs. It looks for changes that often happen around ovulation and uses them to estimate your fertile window and period timing.
Circular estimates your fertile window by reading body signals like temperature and resting heart rate, together with your cycle history. This helps the prediction adjust to your current cycle instead of relying only on a 28-day average.
No. Circular Ring 2 can detect body changes that often happen around ovulation, such as a temperature rise, but it does not medically confirm ovulation. For clinical confirmation, use medical testing or speak with a doctor or fertility specialist.
No. Circular Ring 2 is not a method of contraception or birth control, and its fertile window estimates should not be used to prevent pregnancy.
Circular recommends wearing the ring for 2 to 3 cycles to build a stronger personal baseline. The longer you wear it, the more it learns your normal cycle pattern.
Body temperature often rises slightly after ovulation and stays higher during the luteal phase. Circular tracks temperature automatically, including during sleep, so you do not need to take a manual basal temperature reading every morning.
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.
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.
PCOS can make ovulation and cycle timing harder to predict. Circular Ring 2 can still track your temperature, HRV, resting heart rate, sleep, and cycle patterns over time. The more you wear it, the easier it may become to spot your own patterns, but predictions may be less reliable if your cycles are irregular or if ovulation does not happen every cycle.
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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