Ring size

Ring size 11.5: US 11.5 in mm, UK, EU and Japan

A US size 11.5 ring has an inside diameter of 21.0 mm and an inside circumference of 65.9 mm. The same ring is a W½ in the UK and Australia, a 65.9 on the EU/ISO scale and a 25 in Japan and Korea. The figures below come from the same geometry as the full chart, so they agree with it to a tenth of a millimeter.

US 11.5 in every sizing system

US 11.5 with the half size below and above it, so a measurement that lands between two sizes still has a row to read.
US / CanadaUK / AustraliaEU / ISO (circumference, mm)Japan / KoreaInside diameter (mm)
US 11V½64.62420.6
US 11.5This sizeW½65.92521.0
US 12X½67.22621.4

What a size 11.5 ring measures

Inside diameter 21.0 mm (about 0.83 in), inside circumference 65.9 mm. Measuring a ring that already fits? Measure the inside edge to edge for the diameter. Measuring a finger? Wrap a strip of paper around its base and compare the overlap with the circumference.

Is US 11.5 a common ring size?

Yes. US 11.5 sits inside the 8 to 12 range most men's bands are stocked in. Wider bands in this range often need a half size up, so try the actual width.

Between two sizes?

Take the larger one. A ring is easier to make smaller than larger, a wide band needs a little more room than a thin one, and fingers swell in heat and in the evening. A jeweler's sizer set settles it in a minute.

Convert a measurement to a ring size

Measure a ring that already fits the right finger, or the finger itself, and enter the number in millimeters.

What did you measure?

Quick answers

Frequently asked questions

What is a US ring size 11.5 in mm?

US 11.5 is 21.0 mm across the inside and 65.9 mm around the inside. The millimeter circumference is also the EU/ISO size, 65.9.

What is US 11.5 in UK ring sizes?

US 11.5 is a UK and Australian W½. UK letters step 1.25 mm of circumference at a time, so a half letter is a real difference.

What is US 11.5 in EU ring sizes?

US 11.5 is EU/ISO 65.9. The EU number is the inside circumference in millimeters, so a shop that stocks whole sizes will offer the nearest one.

What is US 11.5 in Japanese and Korean ring sizes?

US 11.5 is a Japanese and Korean 25. Those scales step a third of a millimeter of diameter per number, so they are finer than US half sizes.

Every ring size, US 3 to 13

Conversions are rounded to the nearest standard size, and published charts differ from each other by up to half a size. Treat the result as a close estimate, confirm it with a jeweler's sizer before buying, and check the resizing policy.