Work out ring size converter instantly with clear inputs, formula shown and shareable results.
Ring sizing is fundamentally a circumference measurement: EU sizes are the circumference in millimetres directly, while US sizes run in steps of about 0.8 mm of circumference from a 36.5 mm base at size 3.5. A 17.3 mm inner diameter is 54.3 mm around, roughly a US 7 or a UK N.
Circumference
C = pi x inner diameter
US size
size = (C - 36.5) / 2.55 + 3.5, approximately
Measure the inner diameter of a ring that fits, or wrap a strip of paper around the finger and measure its length as circumference.
Yes - by up to half a size with temperature, time of day and salt intake. Measure warm and at the end of the day.