ABY Jewellery · The sizing guide
A little clarity before your forever piece.
Find your size across international systems.
Choose the size marked on your ring or given by your jeweller.
Don’t know your size? See how to measure ↓Start with the correct finger and hand. A ring that fits one finger may not fit another.
Select your size to see its closest international equivalents.
Measure with care
Use millimetres and measure more than once. Small differences can change the size you choose.
Measurement diagram · not actual size
01 / A ring you already wear
Choose a round ring that comfortably fits the intended finger. Measure straight across its centre, from one inside edge to the other. Exclude the metal. Enter the result under “Inside diameter”. A calliper gives a clearer reading than a ruler.
Measurement diagram · not a printable ruler
02 / An at-home estimate
Wrap a narrow, non-stretch paper strip around the base of your finger without squeezing. Mark the overlap, flatten it and measure the length in mm. Enter “Inside circumference”. Paper can twist or tighten, so treat this as a rough estimate and check the knuckle too.
Fit depends on more than one measurement
03 / Your final fit
A comfortable ring stays secure at the base and passes the knuckle with gentle resistance. For engagement rings, wedding bands or a stack, arrange a fitting with ABY and discuss the actual band width and profile.
Wide bands and stacked rings can feel tighter. Try a similar width; don’t automatically add a fixed half-size.
Fingers can swell in warmth and shrink in the cold. Measure at a comfortable temperature, repeat later in the day, and avoid measuring immediately after exercise.
A larger knuckle, tapered finger or different dominant hand can change fit. If the base and knuckle differ a lot, ask for an in-person assessment.
Fine jewellery that’s about you
Bring your conversion to an ABY consultation. Let’s find a comfortable fit for the ring, the hand and the way you wear it.
Book an ABY consultation ↗Keep the numbers in perspective
HK sizes are the starting rows below. Other systems show the nearest reference size, not exact equivalents.
| HK | US ≈ | UK ≈ | Japan ≈ | Diameter mm | Circumference mm |
|---|---|---|---|---|---|
| 5 | 2.5 | — | 3 | 13.78 | 43.30 |
| 6 | 3 | F½ | 4 | 14.10 | 44.30 |
| 7 | 3.5 | G½ | 5 | 14.48 | 45.50 |
| 8 | 4 | H½ | 6 | 14.80 | 46.50 |
| 9 | 4.5 | I / I½ | 8 | 15.18 | 47.70 |
| 10 | 5 | J | 9 | 15.50 | 48.70 |
| 11 | 5 | K | 10 | 15.88 | 49.90 |
| 12 | 5.5 | K½ / L | 11 | 16.20 | 50.90 |
| 13 | 6 | L½ | 12 | 16.58 | 52.10 |
| 14 | 6.5 | M½ | 13 | 16.90 | 53.10 |
| 15 | 7 | N½ | 14 | 17.28 | 54.30 |
| 16 | 7.5 | O½ | 15 | 17.70 | 55.60 |
| 17 | 8 | P | 16 | 17.98 | 56.50 |
| 18 | 8 | Q | 17 | 18.30 | 57.50 |
| 19 | 8.5 | R | 18 | 18.68 | 58.70 |
| 20 | 9 | R½ | 19 | 19.00 | 59.70 |
| 21 | 9.5 | S½ | 20 | 19.39 | 60.90 |
| 22 | 10 | T½ | 21 | 19.70 | 61.90 |
| 23 | 10.5 | U½ | 22 | 20.09 | 63.10 |
| 24 | 11 | V | 23 | 20.40 | 64.10 |
| 25 | 11.5 | W | 24 | 20.79 | 65.30 |
| 26 | 11.5 | X | 25 | 21.10 | 66.30 |
| 27 | 12 | X½ / Y | 26 | 21.49 | 67.50 |
| 28 | 12.5 | Z | 27 | 21.80 | 68.50 |
| 29 | 13 | Z½ | 29 | 22.19 | 69.70 |
| 30 | 13.5 | Z+1 / Z+2 | 30 | 22.50 | 70.70 |
We compare the circumference behind each size, then show the closest listed size in each system. Measurements are rounded to 2 decimal places. Sources: WILLS (HK), NIWAKA (US & Japan) and Angelic Diamonds (UK). Reference reviewed September 2026.
Buying an ABY piece? This international guide does not replace a product’s size chart. ABY’s older product chart uses different mappings in places. Confirm the sizing convention for your chosen design with ABY before placing an order.
A few things worth knowing
Whether you’re choosing an engagement ring, a wedding band or an everyday piece, use this guide as a starting point to find your most comfortable fit.
Check the system used by the jeweller or the specific product. You may encounter HK, US, UK, Japanese or millimetre-based labels. A size number without a system is ambiguous: HK 13 and Japan 13 are not the same measurement in this guide.
Select Hong Kong (HK), then your known size. The converter finds its reference circumference and compares that measurement with the other systems. For example, HK 13 is 52.1 mm in this reference, closest to US 6 and UK L½. Always check the jeweller’s own chart.
No. The scales use different measurement mappings. Here, HK 13 corresponds to 52.1 mm circumference, while Japan 13 corresponds to 53.41 mm. Choose the named system rather than assuming the same number means the same fit.
Use the nearby sizes shown by the converter as options to try. Don’t choose solely by rounding up or down: the width, inner profile and your knuckle affect the best fit. Ask ABY to assess the intended design, especially for wide bands or stacked rings.
Diameter is the distance across the inside of a round ring. Circumference is the distance around that inside circle. Circumference = diameter × π. For example, a 16.5 mm inside diameter is about 51.84 mm around. Measure the empty space, not the outer metal edge.
Screen sizes, zoom and display scaling vary, so an uncalibrated on-screen circle cannot reliably measure your ring. The diagrams on this page are explanatory only. Use a physical measurement or arrange a fitting with ABY.
