The different international ring measuring units
Every country has its own ring size chart. Here is a breakdown of the most common ring size systems.
In the United States, a number chart is used. The numbers run from zero to sixteen and run in full, quarter, half, and three-quarter sizes. There are two elements that are measured: the inside diameter and the inside circumference. The US uses inches to measure, so the measurements mentioned refer to inches. A size 0 ring is 0.458 inches in diameter and 1.44 inches in inside circumference. A size 16 ring measures 0.97 inches in diameter and 3.05 inches in inside circumference.
South Africa, United Kingdom, Ireland, Australia, and New Zealand
An alphabetized system is used in South Africa, the UK, Ireland, Australia, and New Zealand. A size A ring is equivalent in size to a size 0.5 ring in American terms. The sizes come in full sizes (A) and half sizes (A ½). A size A ring, the smallest size, runs 12.04 mm in diameter and 37.8 mm in inside circumference. The largest size is a size Z4 ring, the only letter size that goes beyond the half size. It is equivalent in size to the American size 14 ½, six sizes smaller than America’s largest ring size. It measures 23.42 mm in diameter and 73.6 mm in inside circumference.
Japan, China, and South America
Like the United States, Japan, China, and South America use numbers to determine ring sizes. However, their system works quite differently. Numbers run from 1 to 27, but are equivalent to only some other international sizes. For instance, the smallest size is a 1, and is equivalent to a US size 1 (the fourth size) and a UK B (the third size.) It measures 12.45 mm in diameter and 39.1 mm in inside circumference. Size 27, the largest size, is comparable with a US size 13 and is somewhere in between a UK Z ½ and a Z2. America has fourteen more sizes larger than a 27, and the UK has four. A size 27 ring measures 22.2 mm in diameter and 69.7 mm in inside circumference.