What is a cm to Ring Size Converter?

A cm to ring size converter is an online tool that helps you figure out your ring size by simply entering a measurement in centimetres—either the diameter of a ring or the circumference of your finger. No need to download anything, print sizing charts, or guess your size ever again.

Here’s how it works: you measure either the diameter (the inside width of a ring) or the circumference (the total distance around your finger) in centimeters. Then, plug that number into this tool, and it instantly converts it into the exact ring size used in various international sizing systems like:

• US / Canada
• UK / Australia
• EU (ISO standard)

Not only does it tell you the closest matching size, but it also shows a visual chart comparing sizes across regions and highlights your result in a detailed size table for reference. So whether you’ve got a ring that fits and want to know its size, or you’re starting from scratch with a finger and a piece of string, this tool has your back. This tool is especially useful if you’re shopping for rings online or buying one as a gift and want to make sure it fits just right.

What makes it even better? It’s fast, accurate, and works right from your phone or computer—no printing out ring sizers or second-guessing conversions.

How to Convert cm to Ring Size?

Converting centimeters to a ring size with this tool is incredibly simple—here’s a quick step-by-step guide:

🧮 1. Measure in cm

You’ll start by choosing what you’re measuring:

• Diameter (inner width of the ring): If you already have a ring that fits perfectly, measure its inside diameter using a ruler.
• Circumference (around your finger): If you don’t have a ring, use a strip of paper or string. Wrap it around the base of your finger, mark where it overlaps, then measure that length.

Tip: Don’t measure too tightly or too loosely—just snug enough to slide over your knuckle.

🔍 2. Enter Your Measurement

• Enter your value (e.g., 5.7 cm) into the tool.
• Select whether you measured diameter or circumference.
• Choose the region you want to convert to—US, UK, or EU ring sizes.

🎯 3. Get Your Size Instantly

Once you hit Convert, the tool will:

• Calculate both diameter and circumference in millimeters and centimeters.
• Find the closest matching ring size from the chart.
• Display your result clearly with size values and label (like US size 7 or UK N½).
• Highlight the matching row in the international size table.
• Show a visual point on the interactive size chart, so you can see where your measurement lands in relation to others.