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Polar Loop with Keely, or Ultrahuman.
Ultrahuman’s rings and the Polar Loop with Keely both give you recovery, sleep and a VO2 max, with no subscription to see your data. Ring AIR is $349 on Ultrahuman’s global store; in the US, Ultrahuman’s site sells the Ring PRO at $479. A Polar Loop is $199.99 once, and Keely is free. Ultrahuman estimates VO2 max from your nights and your day’s activity, with no workout; Keely estimates it only from your walks and runs, and publishes every formula.
Updated
At a glance
| Polar Loop with Keely | Ultrahuman Ring AIR | |
|---|---|---|
| Price | $199.99 for the Loop, once. Keely is free | $349 on Ultrahuman’s global store. In the US, Ultrahuman sells the Ring PRO, at $479 |
| Subscription | None | None to see your data; some features are paid add-ons (PowerPlugs) |
| Worn as | A band on the wrist | A ring |
| Morning | Recovery, 0–100 %: HRV, resting heart rate, sleep, breathing rate and skin temperature | Recovery, from HRV, skin temperature and resting heart rate, updated through the day |
| Effort | Load: points per minute by heart-rate zone, no ceiling, with a target range each morning | Movement Index: your steps, how often you move, and calories |
| Sleep | Stages from the Loop, need (goal, debt and a hard day), consistency and a lights-out time | Sleep Index: how long you slept, resting heart rate and restfulness |
| VO2 max | From your walks and runs: their pace in Apple Health against the Loop’s heart rate, with a likely range | From overnight resting heart rate, daily activity and your details, with no workout |
| An age | Keely Age, from your VO2 max alone, each Monday | Cardio Age, its VO2 max on an age scale. Ultra Age combines Brain, Pulse and Blood Age; Blood Age needs a paid blood test |
| Sensors | Optical heart rate, accelerometer, skin temperature | Optical heart rate, temperature and a 6-axis motion sensor |
| Battery, by the maker | Up to 8 days (Polar’s figure, with Polar Flow) | 4 to 6 days (Ring PRO: up to 15) |
| Phones | iPhone | iPhone and Android |
| Formulas | Every input, weight and constant is published | Inputs are described by Ultrahuman |
| Your data | Raw heart data stays on your iPhone; your account backs up daily summaries | In your Ultrahuman account, with Apple Health sync |
Facts about Ultrahuman come from Ultrahuman’s own pages, checked October 5, 2026. This page compares cost, scores and data; it doesn’t test sensor accuracy.
Where Ultrahuman does more
- A ring. Ring AIR weighs 2.4 g, and some people find a ring easier to wear every night than a band.
- A VO2 max without a walk or run. Ultrahuman estimates it from your nights, your activity and your details, and reports that it typically landed about 4.7 points from a lab test in a study of 101 people.
- An age with more inputs. Ultra Age combines Brain, Pulse and Blood Age, the last from a blood test.
- Add-ons. PowerPlugs such as AFib detection and advanced cycle tracking.
- Android, and Apple Health sync. Keely is iPhone only.
- The Ring PRO’s battery. Up to 15 days, or 45 with its charging case.
Where Keely is different
- It costs less. $199.99 for the Loop, once, against $349 for Ring AIR or $479 for Ring PRO.
- A Load target each morning. Keely counts every minute by its heart-rate zone, with no ceiling, and sets a range for the day from your Recovery and your last four weeks. See Load.
- Stress as a number, live. From 0 to 100 while Keely is open, and never scored while you move. See Stress.
- VO2 max from effort you’ve made. Keely reads the pace you held on your steady walks and runs against the heart rate it took, and shows the likely range. See Fitness.
- Every formula is public, on the methodology page.
- Your raw heart data stays on your iPhone. Only daily summaries are backed up to your account.
Frequently asked questions
Is Keely Age like Ultrahuman’s Cardio Age?
Both start from VO2 max. Cardio Age places Ultrahuman’s estimate on an age scale. Keely Age turns yours into the age whose average mortality risk matches it, about half a year for each point, with its formula on its page.
Does Ultrahuman need a subscription?
Not to see your data, by Ultrahuman’s own store page. Some features, such as advanced cycle tracking, are paid PowerPlugs.
Can I use an Ultrahuman ring with Keely?
No. Keely works with the Polar Loop.
Sources
- Ring AIR: Ultrahuman’s global store and Ring AIR. Ring PRO: Ultrahuman’s US store and Ring PRO.
- Add-ons: PowerPlugs. Scores: the App Store.
- VO2 max: Ultrahuman’s accuracy page (study preprint, July 16, 2026). Cardio Age: Ultrahuman’s accuracy page (July 7, 2026). Ultra Age: Introducing Ultra Age (June 10, 2025).
- Polar Loop price: Polar’s US store. Specifications: Polar Loop user manual.
All checked October 5, 2026. Prices and features change, so check Ultrahuman’s before you buy. Ultrahuman is a trademark of Ultrahuman Healthcare; Keely isn’t affiliated with or endorsed by Ultrahuman or Polar.
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