Ring Size Converter

Buying a ring from a US or European shop when you only know your UK letter size can be confusing. This ring size converter turns UK sizes into US numbers, EU sizes and millimetres, and works the other way too. It uses one consistent chart, based on the systems in this overview of international ring sizes, so every result lines up. If you do not know your size at all, measure your finger with a strip of paper and enter the result in millimetres.

How Ring Size Conversion Works

Every system describes the same thing: the inside of the ring. The UK uses letters, where size A has an inside circumference of 37.8 mm and each full letter adds 1.25 mm, with half sizes in between. The US uses numbers based on inside diameter: 11.63 mm plus 0.8128 mm for each whole size. Most of Europe simply uses the inside circumference in millimetres, so an EU 52 ring measures about 52 mm around the inside.

The converter turns your size into a circumference first, then finds the nearest size in each system. Diameter is circumference divided by pi, roughly 3.1416. For example, UK J is 49.05 mm around, which is closest to US 5 and EU 49. Because sizes are rounded to the nearest half, a conversion can sit a fraction above or below the exact value.

How to Use the Ring Size Converter

Step 1: Choose What You Know

Pick UK size, US size or EU size if you already know one, or Measure if you are starting from a tape or paper strip. Shopping abroad for clothes too? The EU to UK dress size converter handles those labels in the same simple way.

Step 2: Enter Your Size or Measurement

Select your size from the list. To measure, wrap a thin strip of paper around the base of your finger, mark where it overlaps and measure the length in millimetres. You can also measure the inside diameter of a ring that already fits.

Step 3: Read the Conversions

The large letter is your UK size. Below it you will see the US size, EU size, inside diameter and inside circumference.

Step 4: Check Nearby Sizes

The mini chart highlights your size with one half size either side, which helps if you are between sizes or buying a wide band. For shoes, our UK to EU shoe size converter uses the same kind of chart, so you can check both before ordering.

Ring Size Chart: UK, US, EU and mm

US size	Nearest UK size	EU size	Diameter (mm)	Circumference (mm)
3	F	44	14.1	44.2
4	H	47	14.9	46.8
5	J	49	15.7	49.3
6	L	52	16.5	51.9
7	N½	54	17.3	54.4
8	P½	57	18.1	57.0
9	R½	60	18.9	59.5
10	T½	62	19.8	62.1
11	V½	65	20.6	64.6
12	X½	67	21.4	67.2
13	Z½	70	22.2	69.7

Brands do not all use exactly the same chart, and wide bands usually need half a size larger than thin ones. If you are measuring with a strip, remember that the length you mark is the circumference of your finger, not its width. For an engagement ring or an expensive purchase, a professional sizing at a jeweller is the most reliable option.

Frequently Asked Questions