Ring Sizing
ONYX RING
Find your size
Our ring is built to sit snug for accurate tracking — and this chart is calibrated to how it actually fits. Just measure, find your number, and order it. No sizing up.
| Size | Your finger circumference | …or a ring you own (inner Ø) |
|---|---|---|
| 7 | 55.0–57.4 mm | 17.5–18.3 mm |
| 8 | 57.5–59.9 mm | 18.3–19.1 mm |
| 9 | 60.0–62.7 mm | 19.1–20.0 mm |
| 10 | 62.8–65.3 mm | 20.0–20.8 mm |
| 11 | 65.4–67.7 mm | 20.8–21.5 mm |
| 12 | 67.8–71.9 mm | 21.6–22.9 mm |
| 13 | 72.0 mm + | 22.9 mm + |
Right between two sizes? Choose the smaller — snug beats loose. A ring that slides or spins loses contact with your skin (and your data).
How to measure — 30 seconds
Easiest — a ring you already own: take a ring that fits the finger you’ll wear this on, measure straight across the inside in mm (the diameter), and match the “ring you own” column.
Or measure your finger: wrap a thin strip of paper or string snugly around the base of the finger (not the knuckle). Mark where it overlaps, lay it flat, and measure the length in mm. Repeat 2–3 times.
Measure at the end of the day, when your fingers are largest — a cold morning measurement is the #1 reason a ring comes out too big.
Did you get the right fit?
It should feel snug, not tight — secure at the base, comes off with a little soap and water, but doesn’t slide off on its own or spin freely.
Quick test: make a fist — if there’s a gap between the ring and the top of your finger, go one size smaller. Best worn on the index, middle, or ring finger.
Fits sizes 7 and up. Still unsure? Free size exchange — but follow the snug rule and most people nail it first try.