Ring Size CalculatorUK Ring Sizing
Ring Size Chart – UK, US & EU Ring Size Conversion Guide
📊 Complete International Ring Sizing Reference

Ring Size Chart

Compare UK letter sizes, US and Canadian numerical sizes, EU references, inside diameter and circumference in one complete ring size chart. Use the interactive finder to match your measurement, then verify the result with the retailer's own chart before ordering.

🇬🇧 UK A–Z+ 🇺🇸 US / Canada 🇪🇺 EU Reference 📐 Diameter & Circumference
54UK Size Rows
5Reference Columns
½Half Sizes
mm / inMeasurements

💍 How to Use This Ring Size Chart

A ring size chart connects the physical size of a ring with the labels used by different countries and jewellers. The most useful physical references are the ring's inside diameter and inside circumference. Once you know one of those measurements, you can match it to the closest row and compare UK, US/Canada and European size references.

UK ring sizes commonly use letters such as L, M, N, O and P. US and Canadian charts use numbers such as 6, 7 and 8, while European charts commonly use numerical references closely related to circumference. International conversion is not perfectly universal because brands and charts may round differently, so use the chart as a practical guide rather than a guarantee.

For the best result, measure the exact finger and hand or use a well-fitting round ring from that finger. Repeat home measurements, pay attention to knuckle width and band width, and compare the final result with the retailer's own chart before purchase.

🔤 UK letters🔢 US numbers🇪🇺 EU reference📏 Physical measurements

🧮 Ring Size Chart Finder

Find the Nearest Row in the Ring Size Chart

Enter diameter or circumference in millimetres or inches.

✅ Nearest ring-size chart match
—UK Size

📐 Ring Diameter vs Circumference

The two measurements behind every ring size chart

Diameter measures straight across the inside; circumference measures around the inside edge.

INSIDE DIAMETER 17.1 mm INSIDE CIRCUMFERENCE ≈ 53.8 mm Example measurement ≈ UK N
Inside diameterMeasure edge-to-edge across the empty centre of a ring that already fits. Do not include the metal band.
Inside circumferenceMeasure the distance around the inner opening, or estimate finger circumference with a careful non-stretch wrap.
Convert with πCircumference ≈ diameter × 3.14159. Small measurement changes can move the result toward a neighbouring size.
Use the chart as a referenceRetailers can round international conversions differently, so the seller's own chart remains the final ordering reference.
A–F½Very small chart range
G–K½Small chart range
L–Q½Common mid-range sizes
R–W½Larger chart range
X–Z+4Extended large sizes

📊 Complete UK, US & EU Ring Size Chart

UK SizeUS / CanadaEUDiameter (mm)Circumference (mm)Diameter (in)

Conversion note: international size labels are approximate and may vary slightly between jewellers. The physical diameter and circumference are the strongest cross-check.

🌍 How UK, US and EU Ring Size Systems Compare

UK Ring Sizes

The UK system commonly uses letters such as J, K, L, M, N and P, with half sizes available for finer adjustment.

US & Canada

The US and Canadian system uses numerical sizes. Many retailers offer full and half sizes, while some charts include quarter sizes.

EU Ring Sizes

European systems commonly use numerical references closely related to circumference in millimetres, although exact retail labels can vary.

📏 How to Measure for a Ring Size Chart

Measure an existing ring

Choose a round ring that fits the exact finger and hand where the new ring will be worn. Measure straight across the inside opening at its widest point in millimetres. Tiffany's current consumer size guide also describes measuring an existing ring by its interior diameter and matching that measurement to a chart.

Measure finger circumference

Use a narrow non-stretch strip around the base of the finger, mark the overlap and measure the length in millimetres. Repeat the reading because wrap tension and finger condition can introduce error. If the knuckle is noticeably wider than the base, the final ring must still pass over it comfortably.

Measure at a normal hand temperature

GIA notes that temperature, humidity and time of day can affect finger size. Avoid using a reading taken when your hands are unusually cold, hot or swollen.

π Ring Size Chart Formulas

Diameter → CircumferenceCircumference = Diameter × 3.14159Example: 17.12 mm × π ≈ 53.8 mm.
Circumference → DiameterDiameter = Circumference ÷ 3.14159Example: 53.8 mm ÷ π ≈ 17.12 mm.
Millimetres → InchesInches = Millimetres ÷ 25.4Example: 17.12 mm ≈ 0.674 inches.

✅ Why Ring Size Charts Can Differ

Two reputable ring size charts can show a slightly different US or EU equivalent for the same UK letter. This does not necessarily mean one chart is wrong. International conversions can use different rounding rules, quarter-size increments and manufacturer conventions.

  • Rounding: a measurement can be rounded to one decimal place or to the nearest production size.
  • Available increments: one jeweller may make quarter sizes while another only offers full and half sizes.
  • Band construction: wide, comfort-fit, tapered and stone-set rings can feel different on the finger.
  • Home measurement error: paper tension, printer scaling or an oval existing ring can change the reading.
Best practice: use diameter or circumference as the physical cross-check, then confirm the final size with the retailer's own chart. For expensive or difficult-to-resize rings, use professional finger gauges.

📚 Ring Size Standards & Authoritative References

The Gemological Institute of America (GIA) publishes an international ring-size chart and discusses professional finger gauges, knuckle fit and environmental factors that can affect sizing.

ISO 8653:2016 specifies methods for ring-size measurement and designation and notes finger-gauge sets in jeweller-consumer sizing. Tiffany & Co. provides an existing-ring interior-diameter method, while its printable guide instructs users to print at 100% scale before using physical size references.

❓ Ring Size Chart FAQs

How do I read a ring size chart?▼
Find the inside diameter or circumference closest to your measurement, then read across the row for the approximate UK, US/Canada and EU size labels.
What measurement should I use for ring size?▼
The inside diameter of a well-fitting round ring or the circumference of the exact finger are the most useful home measurements.
Are UK and US ring sizes the same?▼
No. UK sizes commonly use letters, while US and Canadian sizes use numbers, so an international conversion chart is needed.
What does EU ring size mean?▼
European ring sizes commonly use numerical references closely related to circumference in millimetres, though retailer labels and rounding can vary.
Why do different ring size charts show different conversions?▼
Charts can round measurements differently and use different size increments. Compare physical diameter or circumference and use the retailer's own chart for the final order.
Can I use diameter instead of circumference?▼
Yes. Measure straight across the inside opening of a well-fitting round ring and match that inside diameter to the chart.
What if I am between two ring sizes?▼
Repeat the measurement, check available half or quarter sizes, and consider the new ring's band width and your knuckle fit.
Do wide rings need a different size?▼
They can. Wide bands often feel more snug than narrow bands, so the best fit may differ even if the size label is the same.
Can I print this ring size chart?▼
You can print the information table, but for true-size physical circles use the dedicated Ring Size Print Guide and verify that it is printed at 100% or Actual Size.
When should I get professionally measured?▼
Use professional sizing for expensive, wide, heavily stone-set or difficult-to-resize rings, or whenever home measurements are inconsistent.
Chart note: size conversions are approximate reference values. Physical measurements and the retailer's own chart should take priority when ordering.