* Ring size conversion
JP 18 ring size conversion
JP 18 is an inside diameter of 18.7 mm (circumference 58.6 mm). In other systems that is US 8.5 = UK Q½ = EU 59 = Japan 18.
Published July 11, 2026
JP 18 — full conversion
- Inside diameter
- 18.7 mm
- Inside circumference
- 58.6 mm
- Japan
- 18
- US / Canada
- 8.5
- UK / Australia
- Q½
- EU (ISO)
- 59
Nearby sizes
- Ø 18.3 mm — US 8.5 = UK Q½ = EU 58 = Japan 17
- Ø 19 mm — US 9 = UK R½ = EU 60 = Japan 19
Buying tips for JP 18
- Wide bands feel tighter — consider going up ~½ US size for bands over 6 mm.
- Printable paper sizers are often ¼–½ size off; prefer a metal gauge at a jeweler.
- Selling the ring for gold? Check 18K ring melt value or the karat × weight calculator.
* Frequently asked
FAQ
- Q. What is JP 18 in other ring size systems?
- A. JP 18 converts to US 8.5 = UK Q½ = EU 59 = Japan 18.
- Q. What is the diameter of JP 18?
- A. Inside diameter 18.7 mm; inside circumference 58.6 mm.
- Q. How should I measure my finger?
- A. Measure at the end of the day when fingers are warm. The ring must clear the knuckle; if knuckle and base differ, size for the knuckle and consider a comfort-fit band.
- Q. Can every ring be resized to this size?
- A. Most gold and platinum bands can move 1–2 sizes. Tension settings, eternity bands, and some titanium/tungsten rings cannot. See a jeweler before ordering a resize.
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