If you already wear rings, simply measure the internal diameter of the ring that fits the finger you want to wear your Lyleu ring on, match it to any of the AUS/UK sizing letters and select the size in the product drop-down menu. If you need to select OTHER, please enter in the Notes at checkout. If you know your size in UK or US sizing, simply convert it to the number or letter next to it. For more detailed instructions, please see the Ring Sizing page.