Enter the ring size or the finger circumference into the calculator to determine the corresponding value.
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Cm To Ring Size Formula
The following formula is used to calculate the ring size for a given finger circumference in centimeters.
R = (C * 10 - 40) / 4
Variables:
- R is the ring size
- C is the finger circumference in centimeters
To calculate the ring size, multiply the finger circumference by 10, subtract 40, and then divide the result by 4.
| Ring Size (US) | Inside Diameter (mm) | Inside Diameter (cm) | Inside Diameter (in) |
|---|---|---|---|
| 3 | 14.10 | 1.410 | 0.555 |
| 3.5 | 14.45 | 1.445 | 0.569 |
| 4 | 14.86 | 1.486 | 0.585 |
| 4.5 | 15.27 | 1.527 | 0.601 |
| 5 | 15.70 | 1.570 | 0.618 |
| 5.5 | 16.10 | 1.610 | 0.634 |
| 6 | 16.51 | 1.651 | 0.651 |
| 6.5 | 16.92 | 1.692 | 0.666 |
| 7 | 17.35 | 1.735 | 0.683 |
| 7.5 | 17.75 | 1.775 | 0.699 |
| 8 | 18.19 | 1.819 | 0.716 |
| 8.5 | 18.53 | 1.853 | 0.730 |
| 9 | 18.89 | 1.889 | 0.744 |
| 9.5 | 19.41 | 1.941 | 0.765 |
| 10 | 19.84 | 1.984 | 0.781 |
| 10.5 | 20.20 | 2.020 | 0.795 |
| 11 | 20.68 | 2.068 | 0.814 |
| 11.5 | 21.08 | 2.108 | 0.829 |
| 12 | 21.49 | 2.149 | 0.845 |
| 13 | 22.33 | 2.233 | 0.880 |
| Approximate values. 1 inch = 25.4 mm. Typical rule of thumb: +1 US size ≈ +0.83 mm in inside diameter. | |||
What is a Ring Size?
Ring size is a measurement used to denote the circumference or diameter of a ring. It is typically measured in millimeters or inches and is used to ensure that a ring fits comfortably on a person’s finger. Ring sizes can vary based on regional standards, but the most common systems include the US, UK, and European sizing charts. Knowing your ring size is essential when purchasing rings, especially for special occasions such as engagements or weddings.
How to Calculate Ring Size?
The following steps outline how to calculate the ring size.
- First, measure the circumference of your finger in centimeters.
- Next, multiply the finger circumference by 10.
- Subtract 40 from the result.
- Finally, divide the result by 4 to get the ring size.
- After inserting the values and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Finger Circumference (C) = 5.5 cm
Ring Size (R) = (5.5 * 10 – 40) / 4 = 2.5