Ring Size Converter

📖 Tool Introduction

Ring Size Converter is a free online tool built for shopping for engagement rings, wedding bands, couple rings and everyday fashion rings. Rings are one of the easiest accessories to order in the wrong size, because China, the United States, Europe and the United Kingdom each use their own numbering system: a Chinese size 16 ring corresponds to a US 8, an EU 55 and a UK P, so a shopper who only reads one country's label on a product page will often pick the wrong band. This tool supports two measurement methods. If you have wrapped a string around your finger and measured the length in millimetres, choose the circumference mode and enter that value. If you already own a ring that fits well and have measured its inner diameter, switch to the diameter mode and enter that instead; the tool multiplies the diameter by pi to get the circumference and then matches it to the closest international band. The result card shows the US, EU, CN and UK sizes side by side, and the matching row in the reference chart below is highlighted so you can see at a glance how your size appears on labels from different countries. A clear at-home measurement guide is included, so anyone can measure accurately with nothing more than a piece of string. All calculations run locally in your browser and no personal measurement data is ever uploaded, so you can check your size in complete privacy. Whether you are surprising a partner with a ring, ordering from an overseas jeweller, or double-checking a size before checkout, this converter removes the confusion of reading four different numbering systems on the same tiny tag.

✨ Key Features

• Two measurement modes: enter either circumference in mm or diameter in mm; diameter is automatically converted via pi
• Four systems at once: US, EU, CN and UK sizes shown together on the result card
• Chart highlighting: the closest row in the international chart is highlighted automatically after conversion
• Full reference chart: 17 common sizes from 47 mm to 64.5 mm circumference included
• At-home measuring guide: step-by-step string-method instructions for first-time shoppers
• Copy and download: copy results to the clipboard or export the chart as CSV for your records

📝 How to Use

1. Choose the circumference or diameter measurement mode
2. Enter the millimetre value you measured with string or an existing ring
3. Click Convert to see the four country sizes on the result card
4. The matching row in the chart below is highlighted so you can compare neighbouring sizes
5. Click Copy result or Download chart to save the result or the full reference table

⚠️ Notes

• Temperature matters: fingers shrink in cold weather and swell in heat, measure at room temperature
• Size up if unsure: if your measurement falls between two sizes, choose the larger one for comfort
• Brand variation: ring width and wall thickness differ by brand; this chart is a general reference, check the brand size page before buying
• Knuckle size: if your knuckle is wider than your finger base, also measure there and pick a size that slides over it comfortably
• Private by design: all conversions run locally in your browser, no finger measurements are uploaded anywhere