Finding the correct ring size is crucial to ensure your ring feels comfortable and looks stunning. Whether you're buying a ring for yourself or planning a surprise for a loved one, this guide will help you measure the perfect ring size from a U.S. perspective.
How to Measure Your Ring Size

Find Your Ring Size
Circumference (mm) | Diameter (mm) | Ring Size (US) |
---|---|---|
44.2 | 14.1 | 3 |
45.5 | 14.5 | 3.5 |
46.8 | 14.9 | 4 |
48 | 15.3 | 4.5 |
49.3 | 15.7 | 5 |
50.6 | 16.1 | 5.5 |
51.9 | 16.5 | 6 |
53.1 | 16.9 | 6.5 |
54.4 | 17.3 | 7 |
55.7 | 17.7 | 7.5 |
Circumference (mm) | Diameter (mm) | Ring Size (US) |
---|---|---|
57 | 18.1 | 8 |
58.3 | 18.5 | 8.5 |
59.5 | 19 | 9 |
60.8 | 19.4 | 9.5 |
62.1 | 19.8 | 10 |
63.4 | 20.2 | 10.5 |
64.6 | 20.6 | 11 |
65.9 | 21 | 11.5 |
67.2 | 21.4 | 12 |
1. Measuring the Internal Diameter of an Existing Ring
One of the easiest ways to determine your ring size is by measuring the internal diameter of a ring that already fits well.
What You Need: A ruler or measuring tape.
- Lay the ruler flat on a table.
- Place the ring on top of the ruler.
- Measure the internal diameter (the part in contact with your finger) in millimeters (mm).
Use a Ring Size Chart: Match your measurement to the corresponding U.S. ring size on a chart.
2. Measuring Your Finger
If you don’t have a ring to measure, you can measure your finger directly.
What You Need: A piece of string, ribbon, or paper and a ruler.
- Wrap the string comfortably around the base of your finger.
- Mark where the ends overlap with a pen or marker.
- Lay the string flat and measure its length in millimeters (mm) using a ruler.
Use a Ring Size Chart: Convert the measurement to a U.S. ring size.
Tips for Surprising Someone with a Ring
Planning a surprise engagement or gift? Use these tips to estimate the recipient’s ring size:
- Borrow a Ring: Sneakily borrow a ring they wear on the intended finger and measure its internal diameter.
- Use Average Sizes: The average U.S. ring size for women is between 6 and 7. For men, it’s between 9 and 10.
Size Categories:
- Extra Small: Size 4-5
- Small: Size 6-7
- Medium: Size 8-9
- Large: Size 10-11
- Extra Large: Size 12+
Additional Tips
- Measure your finger at the end of the day when it is largest.
- Avoid measuring your finger in cold weather, as fingers shrink when cold.
- Ensure the ring size feels snug but not tight.
Final Thoughts
Finding the perfect ring size ensures your ring is comfortable and fits beautifully. Whether you’re buying for yourself or planning a surprise, using these measurement techniques will help you achieve the ideal fit. Remember, lab-grown diamond rings or custom designs deserve a ring size that matches their brilliance and beauty!