Ring Size Converter & Chart

How to Measure Your Ring Size

There are several reliable methods to determine your ring size at home:

Method 1 — Using an existing ring: Take a ring that fits the intended finger comfortably. Place it on a ruler and measure the inside diameter in millimetres. Use the chart above to find your size in any system.

Method 2 — Paper strip method:

1. Cut a thin strip of paper or use a piece of non-stretchy string.
2. Wrap it snugly around the base of the finger, just below the knuckle.
3. Mark where the strip overlaps with a fine pen.
4. Measure the length in millimetres — this is your circumference.
5. Use the converter above to find your ring size.

Method 3 — Professional sizing: Visit a jeweller and ask to be measured with a ring mandrel or sizing gauge. This is the most accurate method, especially for wide bands which typically require a half-size up.

Tips for Accurate Measurement

Fingers change size throughout the day — they are typically smallest in the morning and largest in the evening. Temperature also affects finger size: cold weather causes fingers to shrink, while heat causes swelling. For the most accurate result, measure at room temperature in the afternoon.

If your finger is between two sizes, it is generally better to round up to the larger size. Rings can always be made slightly smaller by a jeweller, but stretching a ring larger can weaken the metal.

For wide bands (6mm and above), order a half-size larger than your standard measurement. The wider the band, the tighter the fit because more metal sits against the finger.

Understanding Ring Size Systems

Different countries use different ring sizing standards, which can cause confusion when ordering internationally. The US/Canada system uses numbered sizes from 1 to 16 in half and quarter increments. The UK/Australia system uses letters from A to Z. European sizes correspond to the inner circumference in millimetres. Japanese sizes use a numbered scale starting from 1. The Swiss system is offset from European by approximately 40.

All systems ultimately map to the same physical measurement: the inner diameter or inner circumference of the ring. Our converter above handles all the cross-referencing so you can order with confidence from any international jeweller.

Comfort Fit vs Standard Fit

A comfort fit ring has a domed interior that slides over the knuckle more easily and feels less restrictive on the finger. These rings typically measure slightly larger on a mandrel than their actual wearing size. A standard fit (also called flat fit) ring has a flat interior and measures true to size. When ordering from Casa Jewels, let us know your preference and we will adjust accordingly.

Also see our Metal Weight Calculator and Diamond Shapes & Size Chart for more jewellery reference tools.