How to find your ring size before you order

Why fit matters more for a smart ring

A normal ring only has to look right. A smart ring also has to sit well against your skin, because it reads your pulse through the finger. Oura says the sensor bumps on its ring should sit snugly against the palm side of your finger, in direct contact with the skin. The same logic applies to any smart ring: too loose and it may spin and read badly, too tight and you will take it off.

Measure with paper or string

You need a strip of paper or a piece of non-stretchy string, a pen and a ruler that shows millimetres.

1. Cut a strip of paper about 1 cm wide and 15 cm long, or use a piece of string.
2. Wrap it once around the base of the finger you plan to wear the ring on. Pull it snug, but not tight.
3. Mark the point where the end meets the strip.
4. Lay the strip flat and measure from the end to your mark in millimetres. That is the circumference of your finger.
5. Repeat on two or three different days and use the largest result, not the smallest.
6. Match the number to the size chart for the ring you are ordering.

A paper measurement is a starting point, not a guarantee. We do not give a conversion chart on this page, because every maker's sizes are slightly different. Use the chart on the product page for the ring you buy. If the strip lands between two sizes, see the knuckle test below.

When to measure

Your fingers are not the same size all day. Oura says fingers are at their smallest when your hands are cold, so warm your hands before you measure. Measuring when your hands are warm, such as in the evening after a normal day, gives a more honest number than measuring first thing in a cold room. That is our practical advice, based on the same idea: a ring that only fits at your smallest will feel tight the rest of the time.

The knuckle test

Your knuckle is usually wider than the base of your finger, so the right ring is a compromise. Oura's advice is to look for a size that slips over your knuckles but is not too loose around the base of your finger. That is the one to pick if two sizes seem close.

Oura's warning signs are a useful checklist for any smart ring:

• Too tight: it will not come off without help, or it will not turn at all at the base of your finger.
• Too loose: it slides off when you relax your hand, or it turns or spins freely on your finger.

Which finger

Oura suggests trying the sizers on different fingers and finding the most comfortable combination of size and finger. Remember that the size changes by finger: your index finger and your ring finger rarely take the same size. Decide the finger first, then measure that one.

Zenlyf sizes and what to do if you are unsure

The Zenlyf Ring comes in US sizes 6 to 13, and you choose your size at checkout. You can cancel a pre-order for a full refund until it is packed. If you are between sizes or unsure, message us on WhatsApp before you order. For comparison, Ultrahuman lists US sizes 5 to 14 on its Nigeria page and offers a free sizing kit with an order, which is a good way to try sizes at home. We have not announced a Zenlyf sizing kit, so ask us first if you need one.

If you also want to see how a ring compares on price and membership, read Zenlyf Ring vs Oura Ring vs Ultrahuman Ring AIR.

Common questions

Keep reading

• Three smart rings compared: price, membership, sizes and delivery
• Smart ring subscriptions: what you pay for after you buy the ring
• Where to buy a smart ring in Nigeria, and what to check before you pay