OTHER · RING SIZE

Ring Size Calculator

Convert finger circumference or diameter to US, UK, EU, and Japan ring sizes. Or look up circumference and diameter from a US size.

Input Method
Measurement

Wrap a strip of paper around your finger and measure

≈ Best match
US 7
Closest standard size
US size7
UK / AU / NZN
EU / ISO (mm circ)54
Japan14
Circumference54.4 mm
Diameter17.3 mm
± Neighbors
One size smallerUS 6.5 (53.1 mm)
One size largerUS 7.5 (55.7 mm)

Ring size recommendations are based on the GIA standard chart. Finger size can change with temperature and time of day — measure in the afternoon for best accuracy.

About This Calculator

Finding the right ring size is essential for a comfortable fit. This calculator converts your finger's inner circumference or diameter to the equivalent US, UK/AU/NZ, EU (ISO), and Japan ring sizes — or works in reverse to tell you the measurements for any US size. All sizes follow the GIA (Gemological Institute of America) standard chart and ISO 8653.

How It Works

Wrap a thin strip of paper around the base of your finger, mark where it overlaps, lay it flat, and measure in millimeters — that is your circumference. Alternatively, measure the inner diameter of a ring that fits well. Enter your measurement below, and the calculator finds the closest standard size and shows the adjacent sizes for reference.

The Formula

circumference = π × diameter

π
3.14159… (ratio of circumference to diameter)

Frequently Asked Questions

How do I measure my ring size at home?
Wrap a thin strip of paper or a flexible measuring tape around the base of your finger. Mark the overlap point, remove the strip, and measure the length in millimeters. That measurement is your inner circumference. For the most accurate fit, measure in the afternoon (fingers swell slightly in the heat) and measure several times to confirm.
Why does the calculator show two neighboring sizes?
Finger size varies slightly throughout the day and with temperature. If your measurement falls between two standard sizes, the smaller size will feel snug and the larger will feel loose — choose based on preference and the ring's intended wear. Wide bands often require sizing up by half a size.
What is the difference between US and EU ring sizes?
US sizes are an arbitrary numerical scale (3–13 in half steps). EU/ISO sizes are the inner circumference in millimeters, so a US 7 ≈ EU 54. UK sizes use an alphabetical scale (A–Z). Japan uses a separate numeric scale (1–30).
Can I convert a US ring size to UK or Japan?
Yes — switch to the "US size → other systems" mode and select your US size. The calculator shows the corresponding UK, EU, and Japan sizes, plus the circumference and diameter in millimeters.

Estimates only. Coverage figures (sq ft/gallon, bag yield, BTU/sq ft) are industry rules of thumb with real-world variance. Verify quantities with your supplier before purchasing.