How to get an accurate blood pressure measurement with Circular Ring 2

Blood pressure is the most condition-sensitive number your ring measures. 

Two readings taken ten minutes apart, in the same body, can differ by more than the gap between two health categories. 

Nothing is wrong with the ring when that happens. Your blood pressure genuinely moved.

This guide covers what to do, what to avoid, and why each rule exists.

🧠 Why your technique matters more here than for any other metric

Circular Ring 2 does not squeeze your artery the way a cuff does. It times how long your pulse wave takes to travel from your heart to your finger, using the ECG sensor for the start of the beat and the PPG sensor for its arrival. That delay is called Pulse Wave Transit Time, and it shortens as your blood pressure rises.

Three consequences follow, and they drive every instruction below.

1. Your blood pressure estimate is only as good as your two signals. The ring is timing an interval of a few hundred milliseconds. If either the ECG or the PPG signal is noisy, that interval is wrong, and so is the number. This is why the sections on signal quality below are not optional extras. They are the measurement.

2. The ring needs a clean run of beats. Movement, poor skin contact or cold fingers spoil individual beats. The app discards them.

3. Your calibration is the reference point for every reading that follows. Transit time alone cannot produce a number in mmHg. Your three cuff readings at setup, and your monthly one after that, are what convert it. A sloppy calibration shifts every estimate you take for the next 30 days.

If you only remember one thing from this article: be strict during calibration.

⏱️ Step 1. The 30 minutes before

Avoid all of the following in the 30 minutes before a measurement:

• Caffeine, including tea and energy drinks
• Nicotine in any form
• Alcohol
• A meal
• Exercise, including walking up a flight of stairs

Each one raises blood pressure for real, so the ring is correct to report a higher number. It just will not be a number that represents your usual state.

Also empty your bladder first. A full bladder adds around 10 mmHg to a reading, which is enough on its own to move you from one classification band to the next.

🪑 Step 2. The 5 minutes before

Sit quietly for five minutes before you start. No phone calls, no email, no conversation.

Then get your position right, and hold it during the whole measurement:

• Back straight and supported by the chair
• Both feet flat on the floor, legs uncrossed
• Both arms resting on a table or armrest, roughly at heart height
• Do not talk, and do not listen actively to someone else talking

Important: whichever arm position you choose, use the same one every time, including during calibration. The height of your hand relative to your heart changes the pressure in your finger, so a reading taken with your hand on your thigh is not directly comparable to one taken with your arm on a high desk.

Documented effect of getting these wrong, from clinical measurement research:

Combine three of these and you can easily add 25 mmHg to a reading that is otherwise perfectly valid.

💍 Step 3. Check how the ring is positioned

Before you start the session:

Confirm in the app settings which hand wears the ring. The app uses this, and a wrong setting affects the signal it expects

The PPG sensor shines light into your finger and reads how much comes back. Anything that disturbs that light path, or reduces blood flow to the finger, weakens the signal.

• Logo on top of your finger, LED sensor underneath, on the palm side of your hand
• Slide the ring onto the fleshy pad of the finger, not over a knuckle or bone. Flesh gives the PPG LED sensor good contact and strong perfusion. Bone degrades both
• Snug, not tight. A loose ring slides and lets ambient light leak in between the sensor and your skin. A ring that is too tight restricts blood flow.
• Warm your hands first. Cold fingers constrict the small vessels in your finger and produce a weak pulse signal. Rub your hands together for a minute or two before starting

• Avoid bright light shining directly on your hand during the measurement, such as direct sunlight or a lamp pointed at your finger

   

✋ Step 4. During the measurement

1. Sit down
2. Remove other rings and watches, and stay away from metal surfaces and other electronics while measuring.
3. Place your hands on your legs to get some support and to avoid hand or arm shaking.
4. Spread the fingers wearing the ring wide apart. Only two things should be touching the ring: the finger it is on, and the fingertip from your other hand.
5. Rest a finger from your opposite hand lightly on the outside of the ring. This closes the electrical circuit the ECG needs. Touch, do not press. Pressing hard compresses the tissue under the sensor and adds noise, which makes the measurement take longer, not shorter.
6. Stay still and breathe normally. Do not hold your breath, and do not take deep deliberate breaths.
7. Stay silent.

A session runs in two phases.

Phase 1. Finding a good signal

The app is not measuring your blood pressure yet. It is checking that both sensors have a usable signal before it starts counting anything.

During this phase you see only the data accuracy indicator. It needs to turn green.

What to do: relax your hand, keep the contact light, and wait. The app is not stuck. If the indicator stays red, the problem is one of the physical points in steps 3 and 4, most often cold hands, a firm press instead of a light touch, or the ring sitting over a knuckle.

Phase 2. Estimating your blood pressure

Once the signal is good, the app starts collecting the 20 accurate beats it needs for an estimate.

You now see two graphs: one for the ECG and one for the PPG. 

Use them as live feedback on your signal quality. When the signal is accurate, a green indicator appears on both graphs at the same time. Both have to be green together, because the estimate depends on timing one against the other.

The counter only advances on heartbeats that pass the quality filter. The session ends once 20 consecutive good beats have been captured, which normally takes about 60 seconds.

If the counter is stuck, your signal is not good enough. Reposition the ring on the fleshy pad of your finger, and stop moving. Then let the counter pick up again.

🔁 Step 5. Calibrate properly, because it decides everything

At setup you enter three readings from a standard cuff monitor. After that, one cuff reading every 30 days keeps the model anchored as your arterial properties change with age, weight, medication and season.

Everything above applies during calibration, plus these cuff-specific rules, which only matter for the cuff and not for the ring:

• Put the cuff on bare skin, never over a sleeve. Over clothing can add anywhere from 5 to 50 mmHg
• Use the right cuff size. A cuff that is too small adds 2 to 10 mmHg
• Support the cuffed arm at heart level on a table, do not hold it up yourself
• Use a validated upper-arm monitor. Wrist and finger cuffs are less reliable references

Two more things that make a calibration hold up:

• Calibrate in the state you usually measure in. If you take most of your readings seated at your desk in the morning, calibrate seated in the morning. The anchor inherits the conditions you set it under
• Take the cuff reading and the ring reading close together, within a few minutes, without changing position between them

📊 What to do afterwards

Read the daily trend, not the single measurement. One elevated reading after a stressful meeting tells you about the meeting. Ten readings over two weeks, all taken under the conditions above, tell you about your blood pressure.

For that reason, keep your habits consistent: same time of day, same posture, same chair where you can.

🛠️ Troubleshooting

The accuracy indicator will not turn green You are still in phase 1, so nothing is being counted yet. Warm your hands, check the ring sits on the fleshy pad and not over a knuckle, spread your fingers so nothing else touches the ring, and lighten your touch. Cold hands and pressing too hard are the two most common causes.

The counter is stuck in phase 2 The signal dropped below the quality bar. Watch the two graphs: both need a green indicator at the same time. Reposition the ring, rest your hands, and stop moving. The counter resumes on its own.

My readings jump around a lot between sessions Compare like with like. Check the sessions were taken in the same posture and hand position, at similar times of day, and that none followed coffee, food, exercise or stress. Blood pressure normally varies through the day, and it is usually lowest during sleep and highest in the hours after waking.

The ring's number does not match my cuff Take both within a few minutes of each other, in the same position, and check the cuff is on bare skin at heart level. If they still differ consistently, recalibrate. A calibration taken under unusual conditions biases every reading until it is replaced.

My readings all look high Recheck the calibration first, then the conditions. If readings stay in the elevated or hypertensive bands under good conditions, that is worth a conversation with your doctor and a validated cuff, not a change you make on your own..

❓ FAQ

Can I measure lying down or walking? No. Measure seated, still and supported. Body position alone changes blood pressure.

Can I rest my hands on my legs during the measurement? Yes, and it helps you stay still. Just keep the ring itself off your leg and clothing, and spread your fingers so only the touching fingertip and the wearing finger are in contact with it.

Which hand should wear the ring? The one set in your app settings, and the same one you calibrated with. Do not switch hands between calibration and measurement.

Why do I see two graphs? One is your ECG, the other your PPG. Blood pressure is estimated from the delay between them, so both need to be clean at the same moment. The green indicator on each graph is your live signal check.

How often should I measure? As often as you like, measurements are unlimited and free. For trend tracking, a consistent daily reading at the same time is worth more than several scattered ones.

Do I still need a cuff if I have the ring? Yes, once a month for calibration, and any time your doctor asks for a clinical reading.

🚫 Not a diagnostic tool

Circular Ring 2 is not a medical device. Blood pressure values in the app are estimates for wellness tracking and trend awareness, not for diagnosis, treatment, or any decision about medication. Always consult a healthcare professional for clinical evaluation.