What ring size is 16 mm?
A 16 mm inner diameter is a US 5.5 — UK K½, EU 51, Japan 10.
Measure again at a different time. If the result stays between sizes, compare band width, knuckle clearance, and the retailer's chart before choosing. A wider band can feel tighter than a narrow one at the same labelled size.
- US
- 5.5
- UK
- K½
- EU
- 51
- Japan
- 10
- Inner diameter, millimetres
- 16
- Circ mm
- 50.3
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Frequently asked questions
Is 16 mm a diameter or circumference?
On this page 16 mm is the inner diameter (the width across the inside of the ring). The matching inner circumference is about 50.3 mm.
I am between sizes — should I size up or down?
Measure again at a different time. If the result stays between sizes, compare band width, knuckle clearance, and the retailer's chart before choosing. A wider band can feel tighter than a narrow one at the same labelled size.
How should I confirm a converted ring size before ordering?
Measure the same finger or a ring that fits with a second method. For an expensive, wide, or non-resizable ring, check the retailer's chart and confirm with a physical sizer or jeweller.
Values computed from the US jewellers’ diameter scale and cross-checked against ISO 8653 — methodology last reviewed 2026-08-27. Methodology