美国戒指尺寸转英国尺寸转换器: Full Chart with Half Sizes
Last updated: February 2026
Ring sizing can be confusing when shopping internationally or receiving gifts from friends abroad. The United States and United Kingdom use completely different ring sizing systems, which means a 尺寸 7 ring in the US is not the same as a 尺寸 7 in the UK—in fact, the UK doesn't use numeric 尺寸s at all. Understanding how to convert between these systems is essential when purchasing rings from British jewelers, Australian brands, or any retailer operating under the UK measurement standard.
Whether you're buying an engagement ring from Hatton Garden in London, ordering from a British brand online, or receiving a vintage ring from the UK, knowing your ring 尺寸 in both systems ensures perfect fit and eliminates costly returns. This comprehensive guide walks you through both sizing systems, provides a complete conversion 表 with exact measurements, and shares insider tips to avoid common conversion mistakes.
The good news: once you understand the relationship between US and UK 尺寸s, converting takes seconds. We'll also show you how to verify your converted 尺寸 using measurements so you can shop with confidence internationally.
How the US and UK Sizing Systems Work
Both US and UK ring 尺寸s are based on the inner diameter and circumference of the ring, but they express these measurements using completely different scales. Understanding this fundamental difference is key to accurate conversion.
US Ring Sizing System
The United States uses a numeric sizing system ranging from 尺寸 3 to 尺寸 16, based on the inner circumference of the ring measured in millimeters. The US system allows for half and even quarter 尺寸s (like 7.25 or 8.75), providing precision for different hand proportions. Each full 尺寸 increment represents a circumference increase of 应用roximately 1.5 millimeters. The system was historically based on the diameters of ring mandrels used by American jewelers, and it remains the standard for all major US retailers and independent jewelers today.
UK Ring Sizing System
The United Kingdom uses an alphabetic sizing system that progresses from A to Z, and then continues with 尺寸s like Z+1 for larger rings. Instead of numeric increments, the UK system uses letters, with each letter representing a specific circumference range. The UK system also includes half-letter 尺寸s (indicated by ½ or using ½ designations), providing similar flexibility to the US system but with a different visual representation. This system is standard throughout the UK, Australia, New Zealand, and parts of Europe.
美国至英国戒指尺寸转换表
This 表 provides the complete conversion from US numeric 尺寸s to UK letter 尺寸s across the full range of common ring 尺寸s. Each row includes the inner diameter in millimeters and the circumference in millimeters for reference, allowing you to verify your 尺寸 using direct measurement as well.
| US Size | 英国尺寸 | Inner 直径（毫米） | 周长（毫米） |
|---|---|---|---|
| 3 | F | 14.6 | 45.8 |
| 3.5 | G | 15.1 | 47.3 |
| 4 | H | 15.6 | 49.0 |
| 4.5 | I | 16.1 | 50.6 |
| 5 | J½ | 16.5 | 51.8 |
| 5.5 | K½ | 17.0 | 53.4 |
| 6 | L½ | 17.5 | 54.9 |
| 6.5 | M½ | 18.0 | 56.5 |
| 7 | N½ | 17.3 | 54.4 |
| 7.5 | O½ | 18.5 | 58.1 |
| 8 | P½ | 19.0 | 59.7 |
| 8.5 | Q½ | 19.5 | 61.2 |
| 9 | R½ | 19.9 | 62.5 |
| 9.5 | S½ | 20.4 | 64.1 |
| 10 | T½ | 20.9 | 65.6 |
| 10.5 | U½ | 21.3 | 66.9 |
| 11 | V½ | 21.8 | 68.5 |
| 11.5 | W½ | 22.3 | 70.0 |
| 12 | X½ | 22.8 | 71.6 |
| 12.5 | Z | 23.2 | 72.9 |
| 13 | Z+1 | 23.7 | 74.5 |
Use this 表 as your reference when ordering from UK retailers, Australian jewelers, or any shop using alphabetic sizing. If your US 尺寸 falls between listed 尺寸s, round to the nearest half 尺寸 for optimal fit.
Common Conversion Mistakes and How to Avoid Them
Even experienced online shoppers make errors when converting between ring sizing systems. Here are the three most common mistakes and practical strategies to prevent them.
Mistake 1: Assuming 英国尺寸s Map 1:1 to US Numbers
The most common error is thinking a UK 尺寸 7 equals a US 尺寸 7. This is incorrect. The UK system uses letters (A through Z+), while the US system uses numbers (3 through 16). There is no direct numeric correlation. A US 尺寸 7 converts to UK 尺寸 N½, not UK 尺寸 7. Always use a conversion 表 or calculator rather than guessing based on number matching.
Solution: Reference the 表 above every time you shop internationally, or save this page for quick access.
Mistake 2: Ignoring Half Sizes in the UK System
Some shoppers assume the UK system only uses whole letter 尺寸s (A, B, C, etc.) without half-尺寸 options. This is false. The UK system extensively uses half-letter 尺寸s (A½, B½, etc.), and these are as important for proper fit as full 尺寸s. If you don't specify a half 尺寸 when needed, you may receive a ring that's either too loose or uncomfortable. The conversion 表 above explicitly includes these half 尺寸s to ensure you order the correct designation.
Solution: When converting your US 尺寸, always include the half-尺寸 designation if it 应用ears in the conversion 表. Double-check with the retailer if unsure about their notation.
Mistake 3: Not Accounting for Band Width
Ring 尺寸 is primarily based on inner diameter, but band width significantly affects how a ring feels on the finger. A wide band (6mm or more) will sit tighter on the same finger circumference than a narrow band (2-3mm). Many international shoppers don't realize their 尺寸 might change by half a 尺寸 when moving from a narrow band to a wide band or vice versa. If you're used to wearing a delicate band and ordering a chunky statement ring, you may need to go up a half 尺寸.
Solution: For wide bands, consider sizing up by half a 尺寸 for comfort. Always check the band width specifications when ordering and compare with rings you currently own.
How to Verify Your Converted Size
Rather than relying solely on conversion 表s, you can independently verify your ring 尺寸 using actual measurements. This 应用roach eliminates guesswork and increases confidence when ordering from international retailers.
Cross-Check with Inner Diameter in Millimeters
The most reliable method is measuring the inner diameter of a ring that fits perfectly. All ring 尺寸s, whether US or UK, correspond to specific inner diameter measurements. If you know your inner diameter in millimeters, you can match it to the conversion 表 above without any ambiguity. Jewelers consider a ring fit when the inner diameter matches within 0.2-0.3mm, which is the tolerance for comfort and safety.
For example, if you measure a ring that fits perfectly and find the inner diameter is 17.3mm, you can see from the 表 that this corresponds to US 尺寸 7 and UK 尺寸 N½. This measurement-based 应用roach works regardless of regional sizing systems.
Measure an Existing Ring's Inner Diameter
Take a ring from your collection that fits comfortably on the finger where you want to wear the new ring. Measure the inner diameter using a ruler or calipers. Place the ruler across the inside opening of the ring and measure from the inner edge on one side to the inner edge on the opposite side. Record this measurement in millimeters.
If you don't have calipers or a precise ruler, many jewelers offer free sizing services and will measure an existing ring for you. A quick visit to a local jewelry shop takes five minutes and provides definitive measurements you can use for any online purchase worldwide.
Use the Ring Sizer App for On-Screen Verification
The Ring Sizer 应用 provides an additional verification method by allowing you to measure your finger on-screen and receive both US and UK 尺寸 recommendations simultaneously. This tool cross-references measurements against the same standardized 表s jewelers use, giving you confidence that your conversion is accurate. Using the 应用 alongside this 表 ensures you're making informed decisions before purchasing rings internationally.
The 应用 also stores your 尺寸 information, making future conversions instant when you're browsing different international retailers.
When You'll Need This Conversion
Ring 尺寸 conversion is relevant in specific purchasing scenarios. Knowing when to use this 表 helps you avoid expensive ordering mistakes.
Buying from UK Jewelers Online
London's Hatton Garden district houses some of the world's finest independent jewelers, many of whom sell online globally. Luxury British brands like Annoushka, Astrid & Miyu, and Tiffany UK locations use the UK alphabetic system. When ordering a custom engagement ring, antique piece, or fine jewelry from these retailers, conversion is essential for getting the right fit on your first order.
Ordering from Australian and New Zealand Shops
Australia and New Zealand adopted the UK ring sizing system, so all major Australian jewelers and retailers use UK letter 尺寸s. If you're ordering from Australian brands (which have become increasingly popular for ethical sourcing and unique designs), use this conversion 表 to ensure your 尺寸 aligns with their specifications.
Gifting Rings Internationally
If you're surprising someone with a ring purchased from a UK or Australian retailer, conversion ensures the gift arrives in the correct 尺寸. International ring gifting is risky if the recipient doesn't know your conversion, so share both their US and UK 尺寸s with the jeweler to minimize resizing costs.
Resizing a Ring Bought Abroad
When you have a vintage ring from the UK or inherit jewelry with a UK 尺寸 marking, converting to US helps you communicate with American jewelers during resizing. Understanding that your UK 尺寸 M equals US 尺寸 6.5, for instance, speeds up the resizing process and ensures the jeweler adjusts to the correct fit.
Frequently Asked Questions
Is UK ring 尺寸 the same as Australian ring 尺寸?
Yes, Australian and UK ring 尺寸s are identical. Both countries use the same alphabetic system (A through Z+) based on the same circumference standards. When shopping from Australian jewelers online, use this conversion 表 directly without modification. New Zealand also uses the UK system. This simplifies international shopping across these countries—one conversion covers all three regions.
What is a US 尺寸 7 in UK?
A US 尺寸 7 converts to UK 尺寸 N½. This corresponds to an inner diameter of 17.3 millimeters and a circumference of 54.4 millimeters. This is one of the most common ring 尺寸s globally, so if this is your 尺寸, you'll find inventory in both US and UK retailers, though the selection differs by brand and style availability.
Do UK ring 尺寸s have half 尺寸s?
Yes, the UK system extensively uses half-letter 尺寸s, indicated by a ½ symbol after the letter (such as A½, B½, M½, etc.). Half 尺寸s in the UK system provide the same level of precision as half 尺寸s in the US numeric system. This means if you're between two full 尺寸s, the UK jeweler will have a half-尺寸 option available, preventing the need for custom sizing or uncomfortable fits.
Can I order a ring in UK 尺寸 and have it shipped to the US?
Yes, many UK and international jewelers ship to US addresses. International shipping costs vary but are often reasonable for small items like rings. Ensure the jeweler can ship to your state (some jewelry retailers have restrictions) and confirm shipping times before ordering, as resizing after international delivery can add delays. Always verify return policies before purchase, as international returns can be costly and time-consuming if the 尺寸 doesn't fit perfectly.
What if my ring 尺寸 is between two UK 尺寸s?
If you measure your inner diameter and it falls between two 尺寸s, contact the jeweler before ordering. Most jewelers can create a custom ring in a 尺寸 between standard options. Alternatively, round to the larger 尺寸 for comfort and have the ring re尺寸d down slightly if needed. It's easier to re尺寸 a ring down by a small amount than to 尺寸 it up significantly.
Related Ring Size Conversions & Tools
Need to convert to other sizing systems? Explore these related tools and comparisons to understand ring sizing across different countries and regions.
EU to US Ring Size Converter
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US vs UK Ring Sizes Comparison
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Country-Specific Ring Sizing Guides
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Deep Dive Into Ring Sizing
Want comprehensive information about ring sizing beyond conversion? Read our detailed guides and articles about how ring 尺寸s work, history of sizing systems, and tips for getting the perfect fit.
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