Ring Sizes: US, UK & EU Conversion Guide
Convert ring sizes between US numeric, UK letter and EU millimeter scales with an at-home paper measuring guide, printable tips and answers to common ring sizing questions.
Ring sizing is one of the most personal size conversions because a difference of half a size can mean the difference between a comfortable fit and a ring that spins or feels too tight. US ring sizes use a numeric scale from about 3 to 13, UK sizes use a letter scale from A to Z, and EU sizes use the inner circumference in millimeters. Our Ring Size Converter lets you toggle between all three systems instantly.
US Ring Size to UK Conversion
The conversion from US numeric to UK letter is not a simple arithmetic formula because each scale uses different increments. A US 5 roughly matches a UK J or K, a US 7 matches a UK O or P, and a US 9 matches a UK T or U. Half sizes on both scales add another layer of complexity, which is why our converter handles the cross-referencing for you based on the exact inner diameter of each size.
EU Ring Size: Understanding Millimeter Measurements
EU ring sizes are expressed as the inner circumference of the ring in millimeters, making them the most straightforward and objective of the three systems. An EU size 52 corresponds to a 52 mm inner circumference, or about a 16.5 mm diameter. This direct measurement approach eliminates the need for arbitrary letter or number scales, and it is the system most often used by professional jewelers internationally for consistency.
Tips for Measuring at Home
Cut a thin strip of paper about 6 inches long and wrap it snugly around the base of your finger. Mark where the paper overlaps, then measure the distance from the start to the mark in millimeters to get your circumference. Compare this measurement to the circumference column in our Ring Size Converter chart, which lists the matching US, UK, and EU sizes for each circumference value.