How to convert ring sizes
Ring size conversion chart
US and EU ring sizes paired with the inner diameter and circumference in millimetres they correspond to. One row per half US size.
| US | EU | Diameter (mm) | Circumference (mm) |
|---|---|---|---|
| 3 | 44 | 14 | 44 |
| 3.5 | 45 | 14.4 | 45.2 |
| 4 | 46 | 14.8 | 46.5 |
| 4.5 | 48 | 15.2 | 47.8 |
| 5 | 49 | 15.6 | 49 |
| 5.5 | 50 | 16 | 50.3 |
| 6 | 52 | 16.4 | 51.5 |
| 6.5 | 53 | 16.8 | 52.8 |
| 7 | 54 | 17.2 | 54 |
| 7.5 | 55 | 17.6 | 55.3 |
| 8 | 57 | 18 | 56.5 |
| 8.5 | 58 | 18.4 | 57.8 |
| 9 | 59 | 18.8 | 59.1 |
| 9.5 | 60 | 19.2 | 60.3 |
| 10 | 62 | 19.6 | 61.6 |
| 10.5 | 63 | 20 | 62.8 |
| 11 | 64 | 20.4 | 64.1 |
| 11.5 | 65 | 20.8 | 65.3 |
| 12 | 67 | 21.2 | 66.6 |
| 12.5 | 68 | 21.6 | 67.9 |
| 13 | 69 | 22 | 69.1 |
Ring sizing must be done on the exact finger and knuckle. Sizes are based on the inside of the band, so measure the inner diameter of a ring that already fits.
The three ways a ring size is stated
Ring sizes are really a measurement of the finger: US sizes follow a numeric scale of inner circumference, EU sizes state the inner circumference in millimetres directly, and metric sizing quotes the diameter or circumference of the band inside. The three describe the same ring, so converting between them is exact.
How to use this ring size converter
Type the value you know — a US size like 7, an EU size like 54, or a millimetre diameter or circumference — and the converter shows the full equivalent. The chart lists every half size so you can compare your own measurement at a glance.
How to measure your ring size at home
The most reliable way is to measure the inside of a ring that already fits: lay it on a ruler and read the inner diameter in millimetres. Alternatively wrap a strip of paper around the base of the finger, mark the overlap and measure it in millimetres — that is the circumference.
Tips for an accurate ring measurement
Measure the specific finger and hand you will wear the ring on — sizes differ between fingers and between your left and right hands. Fingers are larger in warm weather and at the end of the day, so avoid measuring when cold.
Frequently asked questions
How do US and EU ring sizes relate?
The EU size is the inner circumference in millimetres, so it is roughly the US size converted to millimetres plus a small offset. In practice a US 7 corresponds to an EU 54 and a US 10 to an EU 60 — the chart maps each step.
Should I measure the diameter or the circumference?
Either works — they are linked by π. Diameter is easier to measure from a ring you already own, while circumference is what you get from a paper-strip method. Just be consistent: never mix a diameter reading into a circumference field.
Which finger should I measure?
The exact finger you plan to wear the ring on, since ring size varies by finger and by hand. Engagement or wedding rings are traditionally worn on the left ring finger in many countries, but comfort is personal.
Why does my ring size change during the day?
Fingers swell with heat, exercise and later in the day, and shrink when you are cold. Measure in the evening at a normal temperature, and if you are between two sizes, choose the larger for comfort.
Are wide bands the same size as thin ones?
Not exactly — a wide band fits more snugly than a thin band of the same inner diameter. If you are buying a wide band, going up half a size is often recommended by jewellers.