Measured by hand
Smart Ring Database
28 rings on one bench, measured with the same caliper and scale. Sort them, compare up to 4 at true scale, and open the photo behind every reading.
All 28 rings, photographed on the scale from the same height, so their size on screen is directly comparable. Select one to open it.
| Ring | Weightg | Widthmm | Wallmm | Thickestmm | Bumpmm | Innermm | Clearmm | Outermm | |
|---|---|---|---|---|---|---|---|---|---|
| Oura Ring 5Size 9 · Stealth · Subscription required | 2.34 | 6.14 | 2.26 | 2.94 | 0.68 | 18.82 | 18.14 | 23.30 | |
| Omni RingSize 9 | 2.35 | 6.52 | 2.37 | 3.24 | 0.87 | 18.69 | 17.82 | 23.83 | |
| RingConn Gen 2Size 9 · Silver | 2.49 | 6.81 | 2.07 | 3.58 | 1.51 | 19.51 | 18.00 | 23.58 | |
| Leep RingSize 9 | 2.70 | 7.97 | 2.34 | 3.24 | 0.90 | 18.83 | 17.93 | 23.56 | |
| Samsung Galaxy RingSize 10 | 2.79 | 7.01 | 2.77 | 3.53 | 0.76 | 19.72 | 18.96 | 24.74 | |
| Ultrahuman Ring AIR Black MatteSize 9 · Black Matte | 2.85 | 8.19 | 2.54 | 3.61 | 1.07 | 20.05 | 18.98 | 24.96 | |
| Niceboy OneSize 8 · Payment | 2.89 | 4.99 | 2.30 | 2.30 | 0.00 | 17.94 | 17.94 | 22.55 | |
| RingConn Gen 3Size 9 · Black | 2.92 | 6.82 | 2.30 | 4.17 | 1.87 | 19.69 | 17.82 | 24.29 | |
| Tesla Ring G55Size 9 | 2.96 | 7.99 | 3.03 | 3.44 | 0.41 | 18.83 | 18.42 | 24.90 | |
| Circular Ring SlimSize 10 | 3.00 | 8.84 | 2.31 | 4.39 | 2.08 | 20.77 | 18.69 | 25.52 | |
| Ultrahuman Ring AIR Raw TitaniumSize 9 · Raw Titanium | 3.03 | 8.20 | 2.75 | 3.83 | 1.08 | 19.81 | 18.73 | 25.22 | |
| RingConn Gen 2 AirSize 9 · Silver | 3.20 | 6.81 | 2.12 | 3.59 | 1.47 | 19.48 | 18.01 | 23.56 | |
| AliExpress Display RingSize 10 | 3.24 | 7.92 | 2.60 | 2.76 | 0.16 | 19.81 | 19.65 | 25.18 | |
| Oura Ring Gen3 HeritageSize 10 · Black · Subscription required | 3.32 | 7.75 | 2.73 | 4.08 | 1.35 | 19.83 | 18.48 | 25.42 | |
| RingConn Gen 1Size 9 · Matte Silver | 3.40 | 7.79 | 2.32 | 4.10 | 1.78 | 19.49 | 17.71 | 24.20 | |
| Nova RSize 9 | 3.41 | 8.04 | 2.82 | 3.48 | 0.66 | 18.69 | 18.03 | 24.79 | |
| Muse One RingSize 7 · Health + payment | 3.70 | 7.67 | 3.35 | 4.47 | 1.12 | 16.61 | 15.49 | 22.17 | |
| Amazfit Helio RingSize 10 | 3.90 | 8.04 | 2.77 | 3.35 | 0.58 | 19.95 | 19.37 | 25.70 | |
| VIV RingSize 10 | 3.98 | 8.03 | 3.15 | 3.67 | 0.52 | 18.82 | 18.30 | 24.80 | |
| Niceboy One UltraSize 8 · Health + payment | 3.99 | 8.08 | 2.62 | 3.42 | 0.80 | 18.44 | 17.64 | 24.08 | |
| Ultrahuman Ring PROSize 9 · Raw Titanium | 4.04 | 8.18 | 2.57 | 4.71 | 2.14 | 20.31 | 18.17 | 26.05 | |
| Oura Ring 4Size 9 · Stealth · Subscription required | 4.26 | 7.89 | 2.62 | 2.97 | 0.35 | 19.22 | 18.87 | 24.76 | |
| Ultrahuman R1Size 9 · Black Matte | 4.27 | 8.12 | 3.10 | 4.32 | 1.22 | 19.89 | 18.67 | 25.93 | |
| Circular Ring 2Size 9 | 4.41 | 7.88 | 2.86 | 4.02 | 1.16 | 19.07 | 17.91 | 24.90 | |
| Aizo RingSize 10 | 4.79 | 8.43 | 2.22 | 2.89 | 0.67 | 20.23 | 19.56 | 24.67 | |
| Circular Ring PROSize 10 | 4.89 | 9.24 | 3.07 | 5.27 | 2.20 | 20.34 | 18.14 | 26.25 | |
| Pebble Index 01Size 10 · Black · Voice notes | 4.95 | 6.59 | 2.86 | 4.52 | 1.66 | 19.85 | 19.85 | 25.60 | |
| Circul SenseSize not marked | 5.99 | 8.84 | 2.76 | 4.52 | 1.76 | 18.24 | 16.48 | 23.09 |
Missing a smart ring? Suggest it
How to read the numbers
- Type
- Health rings track your body. Payment rings pay by tap. Health + payment does both. Voice rings record notes.
- Weight
- Measured on a 0.01 g scale.
- Band width
- How far the ring runs along your finger.
- Wall thickness
- The thinnest part of the band.
- Thickest point
- The thickest part, through the sensor bump.
- Sensor bump
- How far the sensors or battery section add to the wall. On nearly every ring this stands into the finger space. Calculated: thickest point − wall.
- Inner diameter
- Inside the band, away from the bump.
- Clear inner diameter
- Estimated room left for your finger across the bump. Calculated: inner diameter − bump.
- Outer diameter
- How big the ring looks on your hand.
How I measured
I measured every ring on 5 November 2026 with one Extol Premium digital caliper and one Eldonex pocket scale, both reading to two decimals. A camera above the bench photographed each reading.
- Proof for every value. Select Proof on a ring page to see the display. All 170 photos were checked against the stored values.
- One unit each. A different production unit, size or finish can differ slightly. Some rings here are used.
- Hand measurement. This is a careful bench test, not a lab metrology report. Treat differences of a few hundredths as a tie.
- Non-round rings. Many rings have a flat or thick section, so a single diameter cannot describe them fully.
Before you buy a size
Clear inner diameter and the fit estimate are calculated from my measurements. They are a shortlist tool, not a sizing guarantee. Finger shape, knuckle size and the shape of the bump all change how a ring feels.
Use the maker's sizing kit, then read the Ring Size Guide.
Battery figures are maker claims, not my tests, because battery life changes as a ring ages. Maker figures come from the source named on each ring page. Third-party figures are labelled as published, because I could not confirm them on the maker's own spec sheet.
Some ring pages link to deals. Those are affiliate links and are marked. They never change the measurements.
FAQ
Which smart ring is the lightest?
Oura Ring 5 at 2.34 g in size 9, just ahead of the Omni Ring at 2.35 g.
Is ring size 9 the same across brands?
No. The inner diameter of the size 9 rings I measured ranges from 18.69 to 20.31 mm.
How were the rings measured?
With one digital caliper and one 0.01 g scale, with a photo of every reading.