How Korean ring sizes (호) work
Korean ring sizes are a number plus 호 (ho). This table uses a common diameter-based convention also found in Japanese charts: 1호 is 13.0 mm inside, and each step adds one third of a millimetre (0.33 mm), about 1.05 mm of circumference. Our chart covers 1호 to 30호 (13.0–22.67 mm). Other guides and sellers may use different conventions, so compare their actual measurements.
In this convention, that step is smaller than a US half size (1.28 mm of circumference). Check the inner diameter listed by the seller rather than assuming every chart uses the same values.
US and EU/ISO sizes compared
US ring sizes run from about 3 to 13 in half steps: each full size adds roughly 0.81 mm of inner diameter, or 2.55 mm of circumference, and a US 7 measures 17.32 mm across and 54.4 mm around. The EU or ISO size (ISO 8653) is the inner circumference in millimetres rounded to a whole number, so a US 7 and a Korean 14호 (54.45 mm) are both EU 54.
How to measure your ring size
Measure a ring that already fits that finger. Lay it on a millimetre ruler or use a caliper and read the inner diameter from inside edge to inside edge at the widest point. 17.3 mm points to 14호 or US 7; 18.0 mm to 16호 or US 8.
Without a ring, wrap a narrow paper strip snugly around the base of the finger, mark the overlap and measure that length in millimetres as your circumference. Measure the knuckle too, and make sure a ring can pass over it. Paper measurements are estimates: some Korean sellers list a finger circumference different from the corresponding ring's inner circumference. Follow the seller's measuring instructions or try their ring sizer. A wide band may feel tighter, so ask the seller about its fit.
How this converter calculates, and why charts disagree
Inner diameter (mm) = 12.667 + 호 ÷ 3. Circumference = π × diameter. US size = (circumference − 36.537) ÷ 2.5535, shown before rounding and rounded to the nearest half size. EU/ISO = circumference rounded to a whole number. For 14호 that gives 17.33 mm, 54.45 mm, a calculated US 7.02 (so US 7) and EU 54.
Charts often list the same 호 as two US sizes. One 호 is 0.41 of a US size, so most 호 fall between two US half sizes and must be rounded: 17호, a calculated US 8.25, appears as 8 on one chart and 8.5 on another. Different charts may also use different measurements or conventions. Compare the seller's stated inner diameter in millimetres before ordering.
Brands, half sizes and resizing
Charts may use different size conventions and rounding, so two sellers can give different US sizes for the same 호. Check their stated inner diameter against this table. Korean sellers also offer 프리사이즈 (free-size) open rings.
US retailers sell half sizes, so you can usually find a US size within about 0.6 mm of circumference of your 호. A jeweller can typically resize a plain band by about two US sizes, but eternity bands, tension settings and tungsten, titanium or ceramic rings usually cannot, so order those to your measured size.
Quick reference: the most searched sizes
Straight from the table, with inner diameter and EU/ISO size.
- 7호 = 15.00 mm ≈ US 4 (EU 47)
- 9호 = 15.67 mm ≈ US 5 (EU 49)
- 11호 = 16.33 mm ≈ US 6 (EU 51); 12호 also rounds to US 6
- 14호 = 17.33 mm ≈ US 7 (EU 54)
- 16호 = 18.00 mm ≈ US 8 (EU 57)
- 19호 = 19.00 mm ≈ US 9 (EU 60)
- 21호 = 19.67 mm ≈ US 10 (EU 62)