Lifestyle

Ring Size Calculator — Free 2026

Convert your finger circumference or ring diameter to US, UK, and EU ring sizes instantly.

Circumference (mm) Wrap string around finger and measure Enter a value between 36 and 76 mm.

OR Diameter (mm) Measure inner width of existing ring Enter a value between 11 and 25 mm.

Your Ring Size

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US Size

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UK Size

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EU Size

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Diameter (mm)

How It Works

Enter measurement
Choose measurement type
Read your sizes

Understanding Ring Sizes Worldwide

Ring sizing systems vary across countries, which can make buying rings online or while traveling surprisingly tricky. The three most common systems are the US numerical scale, the UK alphabetical scale, and the European numerical scale (which is simply the inner circumference in millimeters). Understanding these systems and how to accurately measure your finger helps ensure a perfect fit every time.

How Ring Sizing Works

All ring sizing ultimately comes down to one measurement: the inner circumference of the ring, or equivalently, the diameter. The US system assigns numbers (typically 3 to 13 in half-size increments) that correspond to specific circumferences. The UK system uses letters (A through Z and beyond) for the same purpose. The EU system is the simplest: the size number equals the circumference in millimeters. So a ring with a 52 mm circumference is simply EU size 52. For more unit conversions, check our unit converter.

Getting an Accurate Measurement

The most reliable home method is the string or paper strip technique. Wrap it around the base of your finger snugly but not too tight, mark where it meets, and measure the length. For the most accurate results, measure in the afternoon (fingers are slimmest in the morning), at room temperature, and when relaxed. Measure the specific finger you plan to wear the ring on, as each finger can differ by a full size or more. If you are between sizes, always round up for comfort. Another popular method is to use an existing ring that fits well: simply measure its inner diameter with a ruler, then use our calculator to find the corresponding sizes.

When to Resize

If a ring spins freely on your finger, it is too large. If it leaves an indentation or is difficult to remove, it is too small. A well-fitting ring should slide on with slight resistance and come off with a gentle twist. Factors like weight changes, pregnancy, arthritis, and seasonal temperature shifts can all affect your ring size over time. You can also explore our age calculator for another popular lifestyle tool.

Frequently Asked Questions

How do I measure my ring size at home?

Wrap a thin strip of paper or string around your finger snugly. Mark where it overlaps, then measure the length in millimeters. This is your circumference. Enter it into our calculator to find your ring size in US, UK, and EU systems. Alternatively, measure the inner diameter of a ring that fits well.

What is the average ring size?

The average ring size for women is US 6 to 6.5 (circumference about 52 mm). For men, the average is US 9 to 10 (circumference about 60-63 mm). However, ring size varies widely based on finger, hand dominance, and time of day.

Do ring sizes change with temperature?

Yes. Fingers swell in hot weather and shrink in cold weather. The difference can be up to a full ring size. For the most accurate measurement, measure your finger at room temperature in the afternoon when your hands are warm but not swollen from heat or exercise.

How do I convert US ring size to UK?

US and UK ring sizes use different scales. A US size 6 is approximately a UK L or L.5, and a US size 9 is approximately a UK R.5 or S. Our calculator handles these conversions automatically using standard jewelers' lookup tables.