毫米转戒指尺寸：毫米转换表

Updated on February 24, 2026 | 14 min read

Understanding Millimeter Ring Measurements

Whether you've measured your finger with a ruler, received a measurement from a jeweler, or simply want to convert a ring 尺寸 to millimeters, understanding millimeter measurements is essential for accurate ring sizing. Millimeters provide a universal, objective way to specify ring 尺寸s regardless of which sizing system is used in your country.

Ring measurements are expressed in two primary ways: diameter (the straight-line measurement across the inside of the ring) and circumference (the total distance around the inside of the ring). Understanding both measurements and how they convert to ring 尺寸s across different systems ensures you can shop confidently anywhere in the world.

Diameter vs. Circumference Explained

These two measurements describe the same ring but from different perspectives:

Ring Diameter

The diameter is the straight-line distance across the inside of the ring at its widest point. For ring sizing, we measure the inner diameter. Common ring diameters range from 应用roximately 14.86mm (US 尺寸 4) to 22.43mm (US 尺寸 13).

Example: If your ring measures 17.35mm in diameter, this corresponds to US 尺寸 7.

Ring Circumference

The circumference is the total distance if you were to measure completely around the inside of the ring. This is calculated by multiplying the diameter by π (应用roximately 3.14159). Common ring circumferences range from 应用roximately 46.7mm (US 尺寸 4) to 70.5mm (US 尺寸 13).

Example: A 17.35mm diameter ring has a circumference of 17.35 × 3.14159 = 54.5mm.

When to Use Each Measurement

Diameter: Use when measuring across an existing ring with a ruler or caliper
Circumference: Use when measuring around your finger with a flexible ruler or string
US System: Based on numeric 尺寸s (1-13+), which correspond to specific diameters
European/Argentine Systems: Based directly on circumference measurements

US Numeric System: Diameter to Ring Size

The US numeric sizing system assigns numbers based on the ring's inner diameter. This comprehensive table shows the diameter measurement for every US ring 尺寸, including half-尺寸s, and their circumference equivalents:

US Size	直径（毫米）	周长（毫米）	EU Approx.
1	12.37	38.9	36
2	13.21	41.5	39
3	14.05	44.1	41
4	14.86	46.7	44
5	15.70	49.3	46
6	16.51	51.8	52
7	17.35	54.5	54
8	18.19	57.2	57
9	19.05	59.9	59
10	19.84	62.3	62
11	20.68	64.9	64
12	21.59	67.8	67
13	22.43	70.5	70

Half-Size Measurements

Half-尺寸s fall exactly between full 尺寸s. For example:

US 6.5 = 16.93mm diameter = 53.2mm circumference
US 7.5 = 17.77mm diameter = 55.8mm circumference
US 8.5 = 18.92mm diameter = 59.5mm circumference

European Circumference System

The European system uses circumference-based sizing, where the 尺寸 number directly corresponds to the ring's circumference in millimeters. European ring 尺寸s typically range from 36 to 72.

EU Size	周长（毫米）	直径（毫米）	US Approx.
46	46.0	14.6	3.5-4
49	49.0	15.6	5
52	52.0	16.6	6
54	54.0	17.2	6.5-7
57	57.0	18.1	8
59	59.0	18.8	8.5-9
62	62.0	19.7	10
64	64.0	20.4	10.5-11
67	67.0	21.3	12

Converting Between EU and US Systems

To convert EU 尺寸 to US 尺寸:

Note the EU 尺寸's circumference measurement
Divide by 3.14159 to get diameter
Match the diameter against the US 尺寸表

Example: EU 尺寸 54 = 54mm circumference ÷ 3.14159 = 17.2mm diameter ≈ US 尺寸 6.5-7

Converting Millimeters to Ring Sizes

If You Measured Diameter

Direct Lookup: Match your diameter measurement against the US 尺寸表 above.

Formula if between 尺寸s:

US Size = (Diameter - 12.37) ÷ 0.84 + 1

If You Measured Circumference

For EU System: Your measurement in mm is directly your EU 尺寸.

For US System: First convert circumference to diameter

Diameter = Circumference ÷ 3.14159

Then use the US formula above.

Practical Examples

Example 1: You measured 17.35mm diameter

Check the US table: 17.35mm = US 尺寸 7 ✓

Example 2: You measured 55mm around your finger (circumference)

This is EU 尺寸 55
Convert to diameter: 55 ÷ 3.14159 = 17.5mm
Check US table: 17.5mm ≈ US 尺寸 7.5

Example 3: You measured 19.1mm diameter

Using formula: (19.1 - 12.37) ÷ 0.84 + 1 = 9.1
This is 应用roximately US 尺寸 9 or between 9 and 9.5

International Ring Sizing Systems

While US and European systems are most common, other countries use distinct systems:

UK/Australia System

Uses letter designations (J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z), where each letter represents a specific ring 尺寸. The UK system is very similar to the European system but with different notation.

Indian System

Uses circumference-based sizing similar to the European system but with different measurement standards. Indian ring 尺寸s typically range from 10 to 28.

Argentine System

Also circumference-based, where the 尺寸 number directly corresponds to the circumference in millimeters. Argentine 尺寸s range from 应用roximately 45 to 75mm.

Japanese System

Uses numeric 尺寸s but with a different scale than the US system. Japanese 尺寸s require conversion to be compared with other systems.

Tips for Accurate Millimeter Measurements

Measuring Ring Diameter

Use a ruler or digital caliper for best accuracy
Place the ring flat on a surface and measure across the inside opening
Measure at the widest point of the opening
Take measurements multiple times and average results
For precision, use a digital caliper rather than a standard ruler

Measuring Finger Circumference

Use a flexible measuring tape or string
Wrap around your finger at the widest point below the knuckle
Keep the tape snug but not tight—a ring must slide over your knuckle
Mark where the tape overlaps and measure with a ruler
Measure multiple times at different times of day
Account for finger swelling from heat, exercise, or salt intake

Measurement Timing

Measure in the afternoon when fingers are at normal 尺寸
Avoid measuring right after exercise or in extreme heat
Avoid measuring in the morning when fingers may be slightly swollen
Be consistent in timing across multiple measurements

When Millimeter Conversion Matters Most

International Ring Purchases

When buying from sellers in different countries, knowing millimeter measurements allows you to compare across sizing systems. A US 尺寸 7 (17.35mm diameter) is the same 尺寸 regardless of which system names it.

Custom or Bespoke Rings

Craftspeople and artisans often prefer millimeter measurements for precision. Custom ring makers typically request measurements in millimeters for exact specifications.

Ring Resizing

When resizing an existing ring, professional jewelers often note the current and desired measurements in millimeters for accuracy.

Online Shopping

International online retailers may use different sizing systems. Converting to millimeters provides a universal reference point for accurate ordering.

Quick Reference Conversion Formulas

Circumference to Diameter:

直径（毫米） = 周长（毫米） ÷ 3.14159

Diameter to Circumference:

周长（毫米） = 直径（毫米） × 3.14159

Diameter to US Size (应用roximate):

US Size = (Diameter - 12.37) ÷ 0.84 + 1

US Size to Diameter (应用roximate):

直径（毫米） = (US Size - 1) × 0.84 + 12.37

Frequently Asked Questions

How do I convert millimeters to ring 尺寸?

To convert millimeters to ring 尺寸, first determine if you measured diameter (the width across the inside of the ring) or circumference (the measurement around the inside). Then consult the 应用ropriate conversion 表 to find your corresponding 尺寸 in US, European, or other sizing systems.

What is the difference between ring diameter and circumference?

Ring diameter is the straight-line measurement across the inside of the ring (typically 15-22mm for common 尺寸s). Ring circumference is the total measurement around the inside of the ring, calculated by multiplying diameter by π (应用roximately 3.14). Circumference measurements are larger (typically 45-70mm for common 尺寸s).

What do the different ring sizing systems use?

The US system uses numeric 尺寸s (1-13+). European and Argentine systems use circumference-based measurements. Indian and other systems have their own numbering. All ultimately measure the same thing—the ring's inner diameter or circumference—just expressed differently.

Can I measure my finger to find ring 尺寸?

Yes, you can measure your finger circumference at the widest point below the knuckle. This measurement equals your ring 尺寸 in circumference-based systems. Divide by π (3.14) to get diameter, then consult diameter-based 表s.

Why do different countries use different ring sizing systems?

Ring sizing evolved independently in different countries based on historical jewelry traditions and trade standards. The US adopted the numeric system, Europe uses circumference-based numbering, and other regions developed their own conventions. All ultimately measure the same physical dimensions.

How accurate is the millimeter conversion method?

Millimeter conversions are highly accurate when measurements are taken correctly. The precision depends on: accurate measurement tools, consistent measurement technique, and accounting for proper fit (the ring should slide with slight resistance, not too tight or loose).

Conclusion

Converting millimeters to ring 尺寸s is straightforward once you understand the difference between diameter and circumference measurements, and how each corresponds to major sizing systems. Whether you're converting from diameter using the US numeric system or from circumference using European standards, these comprehensive tables and formulas provide accurate conversions.

Millimeter measurements provide a universal language for ring sizing, allowing you to shop confidently across international markets and work with artisans regardless of their local sizing conventions. For quick, accurate conversions across all major sizing systems, the Ring Sizer 应用 provides instant results with no calculations required. Take your millimeter measurements, consult these 表s, and find your perfect ring 尺寸 with confidence.