Quick answer: choose your Smart Zikr Ring by its inner diameter in millimetres. Measure the inside of a ring that already fits, or measure your finger circumference and divide it by 3.14. KELVIOR currently offers 16 and 18 mm in pink, and 18, 20 and 22 mm in black.
A smart ring should feel secure enough not to rotate constantly, but it should also pass over the knuckle without pain. Because fingers change slightly during the day, one careful measurement is more useful than guessing from a usual jewellery size.
What do 16, 18, 20 and 22 mm mean?
These numbers refer to the ring's approximate inside diameter, not the outside width and not your finger's circumference. Place a ruler across the widest internal part of a ring and measure straight from one inside edge to the other.
| Inner diameter | Approximate circumference | Available KELVIOR option |
|---|---|---|
| 16 mm | About 50.3 mm | Pink |
| 18 mm | About 56.5 mm | Pink and black |
| 20 mm | About 62.8 mm | Black |
| 22 mm | About 69.1 mm | Black |
The circumference figures are calculated using circumference = diameter × 3.14. They are useful for checking your measurement, but the direct inside-diameter method is usually the simplest.
Method 1: measure a ring that already fits
- Choose a ring that fits the same finger on which you plan to wear the Smart Zikr Ring.
- Place it flat on a ruler marked in millimetres.
- Measure the empty space inside the ring from one inner edge to the opposite inner edge.
- Do not include the thickness of the ring itself.
- Choose the closest available diameter.
This method is best when the existing ring fits comfortably throughout the day.
Method 2: measure your finger
- Wrap a narrow strip of paper or a non-stretch measuring tape around the base of the finger.
- Keep it comfortably snug; do not pull it tight enough to press into the skin.
- Mark the point where the strip overlaps.
- Measure that length in millimetres. This is the finger circumference.
- Divide the result by 3.14 to estimate the inner diameter you need.
Example: a circumference of 57 mm divided by 3.14 gives about 18.2 mm, so 18 mm is the closest option.
Measure at the right time
- Measure near the end of the day, when fingers are normally a little larger.
- Avoid measuring immediately after exercise, in extreme heat or when your hands are unusually cold.
- Measure two or three times and use the most consistent result.
- If your knuckle is wider than the base of your finger, measure both and choose a size that can pass over the knuckle while remaining secure.
What if you are between two sizes?
If the result falls exactly between two available diameters, consider how you prefer to wear the ring. Choose the larger option if your fingers swell easily or you want to move the ring between fingers. Choose the smaller option only when it still passes over the knuckle comfortably. A smart ring that is too tight can be uncomfortable; one that is too loose may rotate while you press the counting button.
Which finger should you use?
Choose the finger on which pressing the counter feels natural. Many people prefer the index finger because the thumb can reach the button easily, but comfort matters more than a universal rule. Measure the exact finger and hand you intend to use: the same finger can differ slightly between your left and right hand.
Common sizing mistakes
- Measuring the outside diameter instead of the empty inner space.
- Using centimetres and forgetting to convert to millimetres.
- Pulling paper too tightly around the finger.
- Assuming the same size fits every finger.
- Relying only on a country size label without checking the diameter.
Frequently asked questions
Is 18 mm the same in every country?
An 18 mm inner diameter is a physical measurement and does not change. Letter and number size systems differ between countries, which is why measuring in millimetres is the clearest method.
Can I exchange the ring if the size is wrong?
Eligibility depends on the condition of the returned product and the terms of the KELVIOR returns policy. Avoid extended use until you are sure of the fit, keep all packaging and contact KELVIOR promptly if you need help.
Does the ring need to touch the skin tightly?
No. It should sit securely without causing pressure, numbness or pain. Its dhikr counter is operated deliberately; an excessively tight fit is not required.
Next step: review the available colours and sizes on the KELVIOR Smart Zikr Ring product page. You may also find our user and Bluetooth troubleshooting guide useful after choosing your size.