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Equivalent ring size
Convert Australian ring sizes (letters) to US ring sizes (numbers) — and US back to AU instantly
Find your exact US ring size from any Australian letter size. Includes inner diameter in mm, circumference, EU size, and UK/Irish equivalent in every result.
Professional ring size conversion for jewellery shopping, online orders, gift buying, travel, and comparing international ring sizing standards
Convert Australian ring sizes to US ring sizes with full accuracy using the complete AU–US correspondence table used by Australian jewellers. AU sizes run from H to Z+1½ while US sizes run from 3¾ to 13½. Our tool covers all 39 standard sizes with exact inner diameter (mm), circumference (mm), EU, and UK equivalents displayed alongside every result for complete international ring size clarity.
Switch between AU→US and US→AU conversion modes with a single tab click. Know your US ring size from an American jeweller and need the AU equivalent for an Australian store? Or vice versa — have an AU size and need US for an online order? Our tool covers both directions instantly, with full size detail breakdowns including diameter, circumference, and EU/French size in a single lookup.
Essential for anyone buying jewellery online from international retailers, shopping across AU and US platforms, buying rings as gifts for someone in another country, or comparing sizing between Australian and American jewellery brands. AU ring sizes (used in Australia, UK, Ireland, and New Zealand) use a letter system, while US sizes use decimal numbers — making this converter indispensable for cross-border jewellery purchases in 2026.
Select your conversion direction and choose a ring size from the dropdown below
Australia uses a letter-based ring sizing system identical to that used in the United Kingdom, Ireland, and New Zealand. Sizes start at H and progress alphabetically through whole letters and half sizes (H, H½, I, I½…) up to Z+1½, with each half-step representing approximately 0.3–0.4 mm of inner diameter. The US ring sizing system uses decimal numbers, typically from size 3 to size 13½ in quarter-size increments, with each quarter size representing approximately the same 0.4 mm increment. Because both systems measure the same thing — the inner circumference and diameter of a ring — conversion is a fixed lookup between the two scales, with each AU letter corresponding to a specific US number.
The key difference is purely one of labelling convention. AU size M (inner diameter 16.51 mm, circumference 51.87 mm) is identical in physical size to US size 6. AU size P (17.75 mm diameter, 55.76 mm circumference) equals US size 7½. The two systems co-exist because Australia adopted the British sizing tradition inherited through the Commonwealth, while the US developed its own independent numeric scale. Anyone buying rings internationally — from US retailers like Tiffany, Zales, or Amazon US while living in Australia — or from Australian jewellers while living in America — needs this exact AU-to-US correspondence to order the correct size.
All systems measure the same thing: inner circumference = π × inner diameter (mm). AU M: ø16.51 mm × π = 51.87 mm = EU 52 = US 6
Average women's AU ring size: N–P (US 6½–7½, ø16.92–17.75 mm). Average men's AU ring size: T–V (US 9⅝–10⅝, ø19.51–20.32 mm). AU sizing is identical to UK, Irish, and New Zealand sizing.
Complete reference table covering all 39 standard Australian ring sizes with their US equivalents, inner diameter in mm, inner circumference in mm, and EU/French size. All data sourced from the standard AU/UK letter-based ring sizing system.
| AU / UK Size | US Size | EU / French | Inner Diameter (mm) | Inner Circumference (mm) |
|---|---|---|---|---|
| H | 3¾ | 46 | 14.65 mm | 46.02 mm |
| H½ | 4 | 47 | 14.86 mm | 46.68 mm |
| I | 4¼ | 47 | 15.04 mm | 47.25 mm |
| I½ | 4½ | 48 | 15.27 mm | 47.97 mm |
| J | 4⅝ | 48 | 15.40 mm | 48.38 mm |
| J½ | 5 | 49 | 15.70 mm | 49.32 mm |
| K | 5⅛ | 50 | 15.80 mm | 49.64 mm |
| K½ | 5⅜ | 50 | 16.00 mm | 50.27 mm |
| L | 5½ | 51 | 16.10 mm | 50.58 mm |
| L½ | 5⅞ | 52 | 16.41 mm | 51.55 mm |
| M | 6 | 52 | 16.51 mm | 51.87 mm |
| M½ | 6¼ | 53 | 16.71 mm | 52.50 mm |
| N | 6½ | 53 | 16.92 mm | 53.16 mm |
| N½ | 6¾ | 54 | 17.13 mm | 53.82 mm |
| O | 7 | 55 | 17.35 mm | 54.51 mm |
| O½ | 7¼ | 55 | 17.45 mm | 54.82 mm |
| P | 7½ | 56 | 17.75 mm | 55.76 mm |
| P½ | 7¾ | 56 | 17.97 mm | 56.45 mm |
| Q | 8 | 57 | 18.19 mm | 57.15 mm |
| Q½ | 8¼ | 58 | 18.35 mm | 57.65 mm |
| R | 8⅝ | 58 | 18.61 mm | 58.47 mm |
| R½ | 8⅞ | 59 | 18.80 mm | 59.06 mm |
| S | 9⅛ | 60 | 19.10 mm | 60.00 mm |
| S½ | 9⅜ | 61 | 19.31 mm | 60.66 mm |
| T | 9⅝ | 61 | 19.51 mm | 61.29 mm |
| T½ | 10 | 62 | 19.84 mm | 62.33 mm |
| U | 10¼ | 63 | 20.02 mm | 62.89 mm |
| U½ | 10½ | 63 | 20.20 mm | 63.46 mm |
| V | 10⅝ | 64 | 20.32 mm | 63.84 mm |
| V½ | 11 | 65 | 20.68 mm | 64.97 mm |
| W½ | 11⅜ | 66 | 20.94 mm | 65.78 mm |
| X | 11⅝ | 67 | 21.18 mm | 66.54 mm |
| X½ | 11⅞ | 67 | 21.30 mm | 66.92 mm |
| Y | 12 | 68 | 21.49 mm | 67.51 mm |
| Y½ | 12¼ | 68 | 21.69 mm | 68.14 mm |
| Z | 12½ | 69 | 21.89 mm | 68.77 mm |
| Z½ | 12¾ | 69 | 22.10 mm | 69.43 mm |
| Z+1 | 13 | 70 | 22.33 mm | 70.15 mm |
| Z+1½ | 13½ | 71 | 22.60 mm | 71.00 mm |
Australia uses the British/Imperial letter-based ring sizing system, shared with the UK, Ireland, and New Zealand. Sizes progress alphabetically from H (smallest standard size, inner diameter ~14.65 mm) through to Z+1½ (largest standard, ~22.60 mm), with half-size increments throughout. Each full letter step represents approximately 1.25 mm of inner circumference (about 0.4 mm diameter). This system is used by all major Australian jewellers including Michael Hill, Shiels, Bevilles, and independent jewellers nationwide.
The United States uses a numeric ring sizing system developed independently of the British letter system. US sizes range from 3 (approximately 14.1 mm diameter) to 13½ (approximately 22.6 mm diameter), with quarter-size increments. Each full US size step equals approximately 0.8 mm of inner diameter. The US sizing system is also used in Canada and Mexico. Major US retailers — Tiffany & Co., Zales, Kay Jewellers, and Amazon US — all use this numeric scale, making AU-to-US conversion essential for cross-border jewellery shopping.
The average ring size for women in Australia is between N and O (US 6½ to 7), corresponding to an inner diameter of approximately 16.92–17.35 mm and a circumference of 53.16–54.51 mm. These sizes are the most commonly stocked in Australian jewellery stores and online retailers. Ring sizes can vary by finger — the ring finger on the dominant hand is typically slightly larger. Fingers also swell in heat and shrink in cold, so size measurements should ideally be taken at room temperature at the end of the day.
The average ring size for men in Australia is between T and V (US 9⅝ to 10⅝), corresponding to an inner diameter of approximately 19.51–20.32 mm. Men's wedding bands and signet rings are typically sized in this range. Men's fingers are generally wider, so ring width also affects comfort fit — a wider band may require sizing up by half a size to allow the ring to slide comfortably over the knuckle. Comfort-fit rings (with rounded inner edges) also typically fit slightly larger than standard flat-fit rings of the same nominal size.
AU and UK sizes are identical — they use exactly the same letter scale, so an AU size P is the same as a UK size P in any jewellery store. EU/French ring sizes use the inner circumference in millimetres as the size number (e.g., AU P = circumference 55.76 mm ≈ EU 56). Japanese ring sizes use a separate numeric scale starting at 1. Swiss ring sizes are based on circumference minus 40. When ordering from European stores (Pandora EU, etc.), look for the circumference in mm to determine the correct AU/US size, or use our EU conversion in the results panel above.
The most accurate home method: wrap a thin strip of paper or a piece of string around the base of the finger you intend to wear the ring on. Mark where it overlaps, then measure the length with a ruler — this is your inner circumference in mm. Compare against the circumference column in the table above to find your AU and US sizes. Alternatively, measure the inner diameter of a ring that already fits using a ruler or vernier caliper. If you are between sizes, size up. Measure at the end of the day when fingers are slightly larger, and at room temperature.
There is no simple mathematical formula to convert AU letter sizes to US numeric sizes — it is a fixed lookup table. However, a useful starting point: AU M ≈ US 6, and each subsequent AU half-size step ≈ one quarter US size step. So AU N (2 half-steps above M) ≈ US 6½. AU O ≈ US 7. For men's sizes: AU T½ = US 10 exactly. You can work up or down from these anchor points as a quick mental estimate, then verify using the table or our converter above for the exact size before making a purchase.
If you have a ring that already fits the finger correctly, the most accurate sizing method is to measure its inner diameter using a ruler, sliding callipers, or a ring sizing mandrel. Measure across the widest internal point in millimetres. Then look up the diameter in the table above — the row with the nearest inner diameter value is your size. For example, if your ring measures 17.0 mm across internally, the closest size is AU O (17.35 mm) or AU N½ (17.13 mm) — so your size is between N½ and O, and you should try both or size up to O.
The same nominal ring size can fit differently depending on the band's width and profile. A wide band (6 mm or more) fits tighter than a narrow band (2 mm) of the same size because it covers more of the finger surface. For wide bands, size up by half a size in both AU and US systems. Comfort-fit rings (with a rounded interior profile) also fit more loosely than standard flat-fit rings and may require sizing down by half a size. Always check with the jeweller whether a size quote is for a standard or comfort-fit ring, and confirm whether AU or US sizing is being used before placing an online order.
Converting an Australian ring size to a US ring size is a simple table lookup since the two systems use different but fixed scales for the same physical measurement. Here is the complete process:
For converting US to AU, select the US→AU tab above, choose your US numeric size, and the AU letter equivalent is instantly displayed alongside the diameter and circumference. For example, US size 8 = AU Q (inner diameter 18.19 mm, circumference 57.15 mm, EU 57). The bidirectional dropdown calculator above handles all lookups instantly, displaying AU, US, EU, diameter, circumference in mm, and circumference in inches in every single result — giving you everything needed to order a ring confidently from any international jewellery store.
For buying rings on international platforms such as Etsy, Amazon, or brand websites like Tiffany, Pandora, or TOUS, always confirm which sizing system the listing uses before selecting a size. US listings use numeric sizes; Australian and UK listings use letters. Our converter makes cross-border jewellery purchases accurate and stress-free.
The Jewellers Association of Australia (JAA) is the peak industry body representing Australian jewellers and goldsmiths. Their member jewellers follow the standard AU letter-based ring sizing system. Visiting a JAA member jeweller for an in-person ring sizing appointment is the most accurate way to determine your AU ring size before placing any online order, especially for high-value jewellery such as engagement and wedding rings.
Visit JAA →Explore our full library of free conversion tools covering weight, length, area, pressure, energy, time, and sizing — all built for fast, accurate results on any device, fully optimised for both desktop and mobile with complete multi-unit breakdowns in every result panel for professional and everyday use across all industries and applications.
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