Ring Size Guide

How to Measure Your Ring Size  A five-minute guide to getting the right fit the first time. A smart ring is not a piece of jewelry that happens to have a chip inside it. It is wider than a traditional band, it has sensor contacts on the inner surface, and it only works when it stays in steady contact with the underside of your finger. That is why ordering your usual ring size is the single most common reason people end up with a ring that is too tight, too loose, or simply unwearable. Why smart ring sizing is different It is wider.   Most smart rings are 7–8 mm wide, compared with 2–3 mm for a typical ring. A wider band spreads pressure across more of your finger, so the same circumference feels tighter. The inside is not smooth.   Sensor contacts and optical windows take up space, which reduces the usable inner diameter. Fit changes the data.   The optical sensor needs consistent contact with the underside of your finger. A loose ring lets ambient light leak in; an overly tight ring restricts blood flow. Both distort heart rate and blood oxygen readings. The practical rule:   order by your measured finger circumference, not by the size stamped inside a ring you already own. Mountova sizes follow their own scale, and the chart below is the one that applies. Before you measure: timing matters more than technique Late afternoon or evening.   Fingers are at their largest. Morning measurements tend to run small. Room temperature, roughly 68–77°F (20–25°C).   Cold hands shrink. Do not measure right after a cold walk, a swim, or in heavy air conditioning. Your non-dominant hand.   It is usually slightly slimmer and less prone to swelling. Twice, several hours apart.   If the two readings differ by more than 1 mm, measure again on another day. Three ways to measure Method 1 — Paper strip (fastest) Cut a strip of paper about 5 mm (1/4 in) wide, long enough to wrap around your finger. Wrap it around the base of the finger where the ring will sit, not over the knuckle. Pull it snug, but not tight enough to compress the skin. Mark the exact point where the paper overlaps. Lay the strip flat and measure from the end to the mark in millimeters. This is your circumference. Match the result to the chart, then run the knuckle test. Method 2 — An existing ring Measure the   inner diameter , the widest distance across the inside of the band, using a ruler or caliper. Do not measure the outside: metal thickness will throw the result off. Multiply the diameter by 3.14 to get the circumference, then match it to the chart. Method 3 — Sizing kit (most accurate) A set of physical sizing rings removes almost all of the guesswork, because you are testing the real width and thickness instead of a number on paper. Wear the candidate size for a full day, including a workout, a shower, and a night of sleep, before you commit. If a sizing kit is available, use it. It is the most reliable way to avoid a return. Smart ring size chart Mountova size US size Finger circumference 6 5.5 52.2 mm (2.06 in) 7 6.5 55.0 mm (2.17 in) 8 7.5 57.5 mm (2.26 in) 9 9 60.0 mm (2.36 in) 10 11 62.8 mm (2.47 in) 11 12 65.4 mm (2.57 in) Match your measured circumference to the chart and order the corresponding Mountova size. Mountova size labels do not follow standard US ring sizing, so the number engraved inside a ring you already own is not a reliable guide on its own. And because a smart ring is wider and has raised sensor contacts than a plain band, choose the larger size whenever you fall between two. How should a smart ring actually feel? A correct fit passes all five checks It slides over your knuckle with light resistance, not force. It stays on when you shake your hand firmly. You can make a fist without pressure or numbness. No deep mark or redness appears at the base of your finger after an hour of wear. The sensor side sits flush against the underside of your finger, with no visible gap. If it fails the last check, the ring is too loose, no matter how comfortable it feels. Five mistakes to avoid Ordering your regular ring size.   Smart rings are wider and have internal sensors. Size up half to one size. Measuring in the morning.   Fingers are smallest then, and the ring will feel tight by evening. Ignoring your knuckle.   If the ring cannot pass the joint, the base measurement does not matter. Sizing down so it will not fall off.   A tight rigid band restricts circulation and degrades sensor accuracy. Measuring cold hands.   Cold fingers can read half a size smaller than they really are. Frequently asked questions Should I size up or down if I am between two sizes? Size up. Fingers swell with heat, activity, and time of day, and a rigid band has no give. Just confirm that the sensor still sits flush against your skin. Which finger should I wear it on? The index, middle, or ring finger of your non-dominant hand. These offer the most stable sensor contact and the least interference from daily activity. Avoid the thumb and little finger. Can I wear it on my dominant hand? Yes, but expect to need up to half a size larger, and expect more knocks and scratches. Will my ring size change over time? Yes. Weight changes, pregnancy, seasonal temperature, and salt intake all affect it. Re-measure if your ring starts to feel different. What if the ring is slightly loose? A small amount of movement is fine as long as the sensor stays in contact. If you can see light between the sensor and your skin, go down a size or move the ring to a thicker finger. Not sure yet? Order a sizing kit first, or send us your measurement in millimeters and we will recommend a size for you. Get a sizing kit