Free ring sizing tool

Online ring sizer for shoppers and Shopify jewelry stores.

This free ring size tool gives a practical sizing reference and conversion table. For production Shopify stores, Ring Sizer Pro turns the same idea into a guided storefront flow that can map results to real product variants.

Online ring sizer showing calibration, inner diameter measurement, circumference, and a recommended US size

Quick sizing method

  1. Use a ring that fits the intended finger.
  2. Measure the inner diameter in millimeters with a ruler or caliper.
  3. Multiply diameter by 3.1416 to estimate inner circumference.
  4. Match the circumference to the closest row in the table.

At-home sizing can vary by device, ruler accuracy, ring shape, and finger swelling. Jewelers should treat this as a confidence aid, not a professional fitting guarantee.

Want this on Shopify?

Ring Sizer Pro adds a guided finger and existing-ring measurement flow to product pages, shows size results across major systems, and attempts to select the closest Shopify variant.

See Shopify App View Demo

Ring size conversion table

Approximate conversions by inner circumference. For checkout use, always show your store's official sizing policy and return/exchange rules.

US UK EU JP Inner circumference (mm)
5 J 1/2 49 9 49.3
6 L 1/2 52 12 51.9
7 N 1/2 54 14 54.4
8 P 1/2 57 16 57.0
9 R 1/2 59 18 59.5
10 T 1/2 62 20 62.1
11 V 1/2 64 23 64.6
12 Y 67 25 67.2

Last updated: 2026-06-17.

Ring size converter

Convert between US, UK, EU, JP, circumference, and diameter.

Shopify ring sizer

Add a guided size flow to jewelry product pages.

Merchant guide

Learn what a ring size guide should include near checkout.