Use the sizing system shown beside the selector. US, UK and Hong Kong sizes are different.
Measure a ring that comfortably fits the intended finger across its inside centre, excluding the metal edges. Alternatively, ask a jeweller to measure your finger.
Measure when your hands are at a comfortable temperature. The ring should pass over your knuckle comfortably. Wider bands may fit more tightly.
Contact us with your measurement if you are unsure. Do not guess a conversion between sizing systems.