The best smart ring for fertility and cycle tracking

How a ring tracks a cycle at all

Every ring here does the same physical thing: it measures skin temperature at your finger, all night, every night, and looks for the shift that follows ovulation. Oura describes the mechanism plainly — hormonal changes raise body temperature after ovulation and lower it when menstruation begins, and the ring “measures your body temperature every minute, directly from the skin of your finger, while you sleep” (Oura).

A finger worn all night is genuinely well suited to this. You get a long, undisturbed measurement window with no thermometer to remember, which is exactly why one FDA-cleared app went looking for a ring. Our temperature tracking page covers what the sensors actually measure and how each brand describes its own precision.

What none of them do is measure hormones. Every cycle feature on this page is an inference from temperature, heart rate and your own logged dates. That matters most in the next section.

The line between a cycle insight and contraception

The two-subscription problem

This is the part most roundups leave out, and it is the reason this page exists on this site. Using a ring as an FDA-cleared fertility tool means paying twice, and both figures come from Oura's own landing page for the integration:

• Oura Membership is required. Oura states it directly: the membership “is required to use the Natural Cycles integration,” at $5.99 a month in the US ($69.99 a year on the annual plan). Cycle Insights is not on the list of features that keep working without a plan.
• Natural Cycles is its own subscription. Oura's page lists the annual subscription at $149.99 billed yearly, or $21.99 per month, after a 28-day free trial (Oura). Natural Cycles' own FAQ confirms it offers two plans, annual or monthly.

Here is what each ring's required plan costs over one, three and five years.

How we ranked them

Every ring carries its score from our published ring rubric: cost of ownership over three years (30%), evidence of accuracy (25%), claimed battery (15%), sizing and fit (10%), data ownership (10%) and phone support (10%). The rubric is on our methodology page. We have not worn or tested these rings, and we are not clinicians: every pick is labeled Researched.

For this page specifically we ranked on what each brand publishes about its cycle features, and on whether those features are cleared, optional or free. Oura leads on capability despite scoring lowest of the four on cost of ownership, because it is the only ring with an FDA-cleared app route at all.

The picks in context

1. Oura Ring 5 — the only FDA-cleared route

Oura offers Cycle Insights, which it says “uses temperature trends to unlock more accurate insights about your menstrual cycle,” plus a Fertile Window feature. More importantly, it is the one ring that syncs into Natural Cycles: the app “will automatically sync your temperature trend data from your Oura Ring when you wake up in the morning,” removing the oral thermometer from the routine. Natural Cycles also uses Oura's heart rate data to discount nights where temperature was raised by alcohol or stress rather than by the cycle. Oura says its temperature sensors generate 1,440 readings a day and resolve changes as small as 0.13°C (0.23°F). Natural Cycles works with any Oura Ring from Gen 2 onwards.

The costs: Cycle Insights sits behind Oura's membership, Natural Cycles is a second subscription, and Oura's Fertile Window feature is explicitly for conceiving, not for preventing pregnancy. Read our Oura Ring 5 review and the membership cost page before committing.

2. RingConn Gen 3 — cycle predictions with no fee

RingConn lists “Women's Full-Cycle Predictions” on the Gen 3 and describes tracking your cycle patterns to flag upcoming periods and shifts, plus pinpointing a fertile window with an option to keep a partner in the loop. It charges no subscription for any of it, claims up to 14 days on a charge, and is rated IP68 and 10ATM.

What it does not have: any FDA clearance, any integration with a cleared app, and any published validation of its cycle predictions. Treat it as a well-specified tracker rather than a clinical tool. Full detail in our RingConn Gen 3 review.

3. Ultrahuman Ring PRO — the feature sold separately

Ultrahuman's approach is the one we find most honest on pricing: there is no required membership, and cycle tracking is sold as an optional add-on. Its US buy page offers a “Cycle & Ovulation Pro PowerPlug” described as “clinically-validated cycle and ovulation insights, built for all types of cycles,” with a plain “I don't want advanced cycle tracking” option beside it (Ultrahuman US). The global store lists the same thing as a Cycle & Ovulation Plus PowerPlug.

Two cautions. “Clinically-validated” is Ultrahuman's own wording and we could not find a named, published study behind it — Ultrahuman's only published research is an in-house sleep heart rate pilot on the older Ring AIR with six volunteers. And the Ring PRO was still a US pre-order when we checked, shipping “from October 10th onwards.” See what the PowerPlugs cost.

4. Samsung Galaxy Ring — free, if you are on Android

Samsung lists Cycle Tracking among its wearable health features and charges nothing for it, using the ring's skin temperature the same way the others do. There is no fee, a charging case comes in the box, and sizes run 5 to 15.

The catches are the usual Samsung ones: Android only with no iPhone support, a Samsung account required, and some features reserved for Samsung Galaxy phones. We also found no peer-reviewed validation of the Galaxy Ring at all. Our best smart rings for women page covers fit, weight and size range alongside the cycle features.

Side by side

If you are trying to conceive

A fertile-window estimate from overnight temperature is a reasonable planning aid and all four rings offer some version of it. Oura's Fertile Window feature is explicitly designed for this purpose, and it is the feature with the most documentation behind it.

Three practical points:

• Give it cycles, not days. Every one of these features works from your own baseline, which takes at least a full cycle and usually more before the predictions mean much.
• Expect noise. Alcohol, illness, a hot room and a late workout all move skin temperature. Natural Cycles specifically uses Oura heart rate data to discount those nights, which is a point in its favour.
• It is not a diagnostic. If conception is not happening, a clinician has tests a ring does not.

If you are trying to avoid pregnancy

Do not use a ring's own cycle feature for this. Natural Cycles says so about Oura's, and by extension the same applies to every ring here that has no clearance at all: RingConn's predictions, Ultrahuman's PowerPlug and Samsung's Cycle Tracking are not contraception.

The only route on this page that is cleared for that purpose is Natural Cycles as the app, with an Oura ring feeding it temperature. Natural Cycles reports 98% effectiveness with perfect use and 93% with typical use, says it can be used with irregular cycles, and is a regulated medical device. It costs a subscription, and Oura's membership is required on top. Discuss it with a clinician the way you would any other method.

What to check before you buy

1. Whether the feature you want is behind a fee. Oura's Cycle Insights is. RingConn's is not. Ultrahuman sells its version as an add-on. Samsung includes it. That is four different pricing models for one feature.
2. Whether you need clearance or just information. Contraception needs the cleared app. Curiosity about your own cycle does not.
3. Your phone. Samsung is Android only. Oura and RingConn support both. Ultrahuman does not publish Ring PRO phone requirements at all.
4. Your size, from the brand's own kit. No brand claims its sizes match another's, and a ring that is loose reads temperature badly. Our sizing guide covers it, and which finger matters more than people expect.
5. What happens to the data. Cycle data is sensitive. Natural Cycles points to its own data-protection program; check what your ring maker says too. Our data privacy guide goes through each policy.

Mistakes to avoid

• Budgeting for one subscription when the cleared route needs two. Oura's membership plus Natural Cycles is roughly $220 a year on the annual plans, by Oura's own figures.
• Treating a fertile-window estimate as contraception. Natural Cycles states plainly that Oura's is not intended to prevent pregnancy.
• Reading “clinically-validated” as “FDA-cleared.” They are different claims. Only Natural Cycles has the clearance here.
• Buying a ring for a feature that needs a phone you do not own. The Galaxy Ring will not work with an iPhone at any price.
• Expecting hormone data. No ring measures hormones. Everything here is inferred from temperature, heart rate and your own logged dates.