Key takeaways
- A smart ring measures your body with green, red and infrared LEDs, a temperature sensor and a 3D accelerometer.
- Current smart rings last 5 to 10 days per charge.
- Most leading smart rings are water resistant to 100 m, so they can stay on in the shower and the pool.
- Oura needs a paid membership for most data, while RingConn and QALO rings work with no subscription.
A smart ring is a wearable health tracker shaped like a ring that measures sleep, heart rate, body temperature and movement from the base of your finger and shows the results in a phone app. This guide covers what a smart ring tracks, the sensors inside one and how they work, what smart rings are used for, battery life, water resistance, subscription fees, and what a smart ring cannot do.
What does a smart ring track?
A smart ring tracks 6 core types of data: sleep, heart rate, heart rate variability, skin temperature, blood oxygen and activity. The app turns those readings into daily scores for sleep, recovery and movement.
- Sleep. Time asleep, sleep stages and how restful the night was.
- Heart rate. Resting heart rate overnight and, on many rings, heart rate through the day.
- Heart rate variability (HRV). HRV is the variation in time between heartbeats. Higher HRV generally signals good recovery.
- Skin temperature. Changes from your normal temperature, which can point to illness or cycle phases.
- Blood oxygen (SpO2). SpO2 is the share of oxygen-carrying red blood cells, usually measured during sleep.
- Activity. Steps, movement and workouts.
Oura says its ring measures more than 50 health and wellness metrics built from these readings. Our guide on what the Oura Ring tracks explains each one.
How does a smart ring work?
A smart ring works by shining light into the skin of your finger and reading how much comes back, while a temperature sensor and a motion sensor record body heat and movement. A small battery powers the sensors, and Bluetooth sends the data to your phone.
The Oura Ring 5 shows the 4 sensor types most rings use:
| Sensor | What it measures |
|---|---|
| Green and infrared LEDs | Heart rate, HRV and breathing rate |
| Red and infrared LEDs | Blood oxygen (SpO2) and nighttime breathing disturbances |
| Digital temperature sensor | Body temperature changes |
| 3D accelerometer | Movement, workouts and sleep stages |
The light-based method is called photoplethysmography (PPG): blood absorbs light differently as it pulses, so the sensor reads each heartbeat. The ring must sit snugly so the sensors keep contact with the skin.
What are smart rings used for?
Smart rings are used for 4 main jobs: tracking sleep, watching recovery and stress, logging daily activity, and spotting changes in the body, such as a rising temperature, before you feel them.
A ring suits people who dislike wearing a watch to bed, because it is small enough to forget about overnight. Rings also suit people who want health data without a screen buzzing with notifications. Women's health features are common too: Oura offers cycle insights with period prediction and a fertile window.
How long does a smart ring battery last?
A smart ring battery lasts 5 to 10 days per charge on current models. Battery life depends on ring size, because bigger rings hold bigger batteries, and on which features are switched on.
| Ring | Battery life | Charging |
|---|---|---|
| RingConn Gen 2 Air | Up to 10 days | About 90 minutes on a magnetic dock |
| Oura Ring 5 | 6 to 9 days | About 80 minutes |
| Oura Ring 4 | 5 to 8 days | 20 to 80 minutes |
| QALO SR-2 | Up to 5 days | 60 minutes, charging case included |
Oura says to start the night with at least 30 percent battery to get Sleep and Readiness scores, so a short top-up before bed helps when the battery is low.
Are smart rings waterproof?
Most smart rings are water resistant, not fully waterproof. The leading models are rated to 100 m, which covers showers, swimming and dishwashing, but the charging dock is not water resistant.
Oura Ring 4 and Oura Ring 5 are rated to 100 m, Oura Ring 5 carries an IP68 rating for dust and water, and the RingConn Gen 2 Air is IP68 rated to 100 m. Oura says its ratings are tested in still fresh water. Rinse the ring after a chlorinated pool or the ocean, and dry it before charging.
Do smart rings have a monthly fee?
Some smart rings have a monthly fee and some do not. Oura needs a paid Oura Membership for most of its data, while RingConn and QALO rings show every tracking feature in a free app.
Without a membership, the Oura app shows only 3 daily scores (Sleep, Readiness and Activity), the ring's battery level and Explore content. Sleep stages, heart rate trends, stress, heart health and cycle insights all need the membership, which is sold monthly or yearly, and new members get the first month free. Add the membership to the cost of the ring when you compare models.
What can't a smart ring do?
A smart ring cannot show notifications, the time or maps, because it has no screen, and it is not a medical device. Oura states that its ring is not intended to diagnose, treat, cure or prevent any disease.
Treat ring data as a trend tracker. A rising resting heart rate or temperature is a sign to rest or to see a doctor, not a diagnosis. Ring sizing is also stricter than with a watch: brands use their own sizes, so a sizing kit comes before the ring. Our Oura Ring size guide explains how to choose. To compare models, see our best smart rings buying guide, and our RingConn Gen 2 review covers a popular ring with no subscription.
Common questions
Can a smart ring replace a smartwatch?
For health tracking, often yes. A smart ring tracks sleep, heart rate and activity, but it has no screen, so it cannot show notifications, maps or the time.
Do smart rings work without a phone?
They record without a phone and sync later. Oura Ring 4 stores up to 7 days of data and Oura Ring 5 up to 3 days, but you need the phone app to see your results.
Which finger should I wear a smart ring on?
Oura recommends the index finger for the most accurate results. The middle and ring fingers also work, as long as the knuckle is not much wider than the base of the finger.
Writes guides and reviews for ProductHunter.
