Some smart rings come in standard sizes, but there is variation, and half sizes are rare, so it’s worth taking some time to ensure you get the correct ring size. Most manufacturers will send you a free sizing kit, enabling you to wear a dummy ring for 24 hours. (You may have to buy the ring directly from the manufacturer to get this kit for free.) You should absolutely do this. Bear in mind that your fingers swell and shrink throughout the day. Your smart ring should be snug to enable the sensors to measure accurately, but you will have to remove it regularly to charge, so you don’t want too tight a fit.

You can wear your smart ring on any finger, but most manufacturers recommend wearing it on your index finger, though the middle or ring finger can also work. These three fingers all have large blood vessels for more accurate pulse monitoring. What’s really important is that the ring fits tightly and securely around the base of your chosen finger, so if you have a big knuckle and a narrower finger base (more common with the middle or ring finger), this can be tricky. I recommend wearing it on the index finger of your less dominant hand because I found wearing it on my right index finger, as a right-handed person, led to more damage on the ring and scrapes on some things I touched.

All the smart rings we tested combined tough titanium with a sensor array on the inside, but the coatings and colors vary. If you are hard on rings, a silver or gold finish will likely suit you best, as there is less risk of damage. My Oura and Ultrahuman rings with black finishes have visible scratches and chips after a few months. The Oura and Amazfit rings have tiny dimples to help you align the sensors. While I prefer the smooth finish of the Ultrahuman, I suspect correct placement aids accuracy enormously.

Most smart rings are durable, but if you want to avoid damage, you should remove your ring when working with tools, weight lifting, washing pots and pans, or even cleaning the sink. If your ring is likely to rub against a surface, take it off. I found this was a bigger problem wearing a ring on my index finger than with the middle or ring finger. I scratched the Oura and Ultrahuman rings when gardening, moving boxes, and using a dumbbell. Titanium is also tough enough to damage surfaces in your home. I gouged the porcelain of my sink and marked the inside of a mug with the angular Ringconn. All the smart rings we tested are water resistant, so you can swim or shower without taking them off.

Photograph: Simon Hill

Smart rings come with a charger and cable, but you will generally have to provide your own wall adapter. From dead, they take anywhere from an hour and a half to three hours to fully charge, but you should avoid letting the battery run down completely, or you run the risk of losing health data. We tested the smart rings above with all the bells and whistles turned on, so our battery life estimates are lower than the manufacturer’s claims.

Most smart rings will track your sleep, heart rate, and temperature. If you want to keep an eye on your sleep and get health insights unobtrusively and comfortably, smart rings are ideal. Fitness tracking varies, with most smart rings offering basic step counts and movement, some offering manual workout tracking, and others offering automatic workout recognition. But you can expect more depth and accuracy from a traditional fitness tracker or smartwatch. Combining a smart ring with an Apple Watch or Fitbit makes for a seamless experience, allowing you to take off the watch and let it charge at night without gaps in your tracking.

In the past few years, we’ve fielded many questions about why someone would get a smart ring instead of, or in addition to, a regular fitness tracker. Here are a few reasons why you might consider it:

Better battery life. A smart ring is smaller and usually (if not always) has better battery life. It’s a helpful addition to your repertoire if you hate missing a couple hundred, or a thousand, steps while you’re charging your smartwatch every day.

Sleep tracking. It’s no coincidence that our favorite sleep tracker is a small, unobtrusive ring. Maybe you’re tired of having your enormous Apple Watch Ultra smack you in the face every time you turn over. (Or maybe you’re charging it instead!)

Cycle tracking. Many watches and fitness trackers now feature a skin temperature sensor that’s sensitive enough to detect when you’re sick or drinking alcohol. However, in Adrienne’s testing so far, only the Samsung Galaxy Ring and the Oura have been accurate enough to track her menstrual cycle.

Finally, fashion. Watches are a statement and a status symbol; a smartwatch often says nothing more about your preferences and choices besides “I don’t like missing meetings.” Almost everyone we know who has bought a smart ring has done so because they have a hand-me-down Cartier Tank, or a fun Casio or Swatch, that they don’t want to give up. If this is you, good for you! And get a ring!

We have been wearing smart rings continuously for several years (sometimes two or three at a time), so we have a good handle on what makes a smart ring worth buying. Every smart ring we test has been worn for at least a month, usually longer, and we always compare its tracking data against our top pick (Oura) and with other smartwatches and fitness trackers (Apple Watch).

We will be testing the Circular Ring 2 ($239).