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Polar Loop with Keely, or WHOOP.
Both give you a Recovery score from 0 to 100 % each morning, a measure of the day’s effort, sleep against your need, a VO2 max estimate and an age for your fitness. WHOOP is a membership, from $199 a year with the band included, and WHOOP Age needs its Peak or Life tier. A Polar Loop is $199.99 once, and Keely is free. WHOOP measures more, including blood oxygen; Keely publishes every formula and keeps your raw heart data on your iPhone.
Updated
At a glance
| Polar Loop with Keely | WHOOP 5.0 and MG | |
|---|---|---|
| Price (US) | $199.99 for the Loop, once. Keely is free | A membership with the band included: One $199, Peak $239 or Life $359 a year |
| Subscription | None | Required. You join for 12 months (new members can choose 24); monthly billing comes only at renewal |
| Morning score | Recovery, 0–100 %: Primed, Balanced or Restore | Recovery, 0–100 %: green, yellow or red |
| What it weighs | HRV, resting heart rate, sleep, breathing rate and skin temperature | HRV, resting heart rate, sleep, respiratory rate, blood oxygen and skin temperature |
| Effort | Load: points per minute by heart-rate zone, linear with no ceiling, and a target range each morning | Strain: 0–21, logarithmic by design, from heart-rate zones and muscular load |
| Stress | Live, 0–100, still or moving | Stress Monitor, 0–3, on Peak and Life |
| Sleep | Stages from the Loop, need (goal, debt and a hard day), consistency and a lights-out time | Sleep performance, need (baseline, strain, debt and naps), consistency |
| VO2 max | From your walks and runs: their pace in Apple Health against the Loop’s heart rate, with a likely range | On every tier: estimated from sleep-time signals, activity and your profile, sharpened by a GPS run or a lab test, updated weekly |
| An age | Keely Age, from your VO2 max alone, each Monday | WHOOP Age, from nine measures of sleep, strain and fitness, weekly, with a Pace of Aging. Peak and Life |
| Formulas | Every input, weight and constant is published | Inputs are described; WHOOP says the weights aren’t published |
| Sensors | Optical heart rate, accelerometer, skin temperature | Adds blood oxygen; WHOOP MG adds an ECG |
| Battery, by the maker | Up to 8 days (Polar’s figure, with Polar Flow) | 14+ days |
| Alarm | None: the Loop can’t vibrate | Haptic alarm |
| Your data | Raw heart data stays on your iPhone; your account backs up daily summaries | Stored in your WHOOP account, with a CSV export and a developer API |
Facts about WHOOP come from WHOOP’s own pages, checked October 5, 2026. This page compares cost, scores and data; it doesn’t test sensor accuracy.
Cost over two years
At today’s US prices, with no discounts:
| First year | Two years | |
|---|---|---|
| Polar Loop with Keely | $199.99 | $199.99 |
| WHOOP One | $199 | $398 |
| WHOOP Peak | $239 | $478 |
| WHOOP Life | $359 | $718 |
Where WHOOP does more
- More sensing. Blood oxygen, measured on every tier and shown on Peak and Life. WHOOP MG, on the Life tier, adds an FDA-cleared ECG (Heart Screener), on-demand AFib detection and Blood Pressure Insights.
- A VO2 max without a run. WHOOP estimates it for every member after 14 recoveries in 21 days, from sleep-time signals, activity and your profile; a 15-minute GPS run or a lab test sharpens it. Keely needs 3 steady walks or runs that another app or watch saves to Apple Health.
- An age from more than fitness. WHOOP Age weighs nine measures, from hours of sleep and daily steps to resting heart rate, VO2 max and lean body mass, and Pace of Aging shows how fast it’s moving. Keely Age comes from your VO2 max alone.
- A haptic alarm. The Loop has no vibration motor, so it can’t wake you silently.
- Battery. 14+ days, and on Peak and Life a PowerPack that charges the band on your wrist.
- More features. AI coaching, a strength trainer and hormonal insights.
- Your data, out. A CSV export, a developer API, and Strava in both directions. Keely doesn’t export yet.
- Where you wear it. WHOOP’s sensor also fits its own garments and a bicep band.
Where Keely is different
- No subscription. You buy the Loop once, and Keely is free, Keely Age included.
- Every formula is public. Recovery’s weights, Load’s points and every constant are on the methodology page, so any number can be checked.
- Load has no ceiling. WHOOP describes Strain as logarithmic: two workouts of 10 don’t add up to 20. Keely’s Load is linear, so twice the work is twice the Load, and each morning brings a target range set by your Recovery.
- Stress from 0 to 100, day and night. Live from the Loop while Keely is open, and read from heart rate alone while you move. See Stress.
- VO2 max from effort you’ve made. Keely reads the pace you held on your walks and runs against the heart rate it took, and shows its likely range. Keely Age turns it into years with a formula on its page. See Fitness.
- Your raw heart data stays on your iPhone. Only daily summaries are backed up to your account.
Frequently asked questions
Is the Polar Loop with Keely a WHOOP alternative without a subscription?
Yes. You buy the Loop once, and Keely turns it into a morning Recovery score, a Load target, live stress, sleep against your need, a VO2 max estimate and Keely Age, free. WHOOP includes its band in a membership that starts at $199 a year.
Is Keely’s Recovery the same as WHOOP’s?
Both run from 0 to 100 % and both lean on HRV and resting heart rate, but they’re different calculations, so the numbers won’t match. Keely’s weights and formula are on its Recovery page.
Is Load the same as Strain?
No. Strain runs from 0 to 21 on a logarithmic scale, so each point is harder to earn than the last. Load counts every minute by its heart-rate zone with no ceiling: an hour in Zone 2 is about 120, and three hours about 360.
Is Keely Age the same as WHOOP Age?
No. WHOOP Age combines nine measures across sleep, strain and fitness, and is on WHOOP’s Peak and Life tiers. Keely Age comes from your VO2 max alone, turned into years through the evidence on fitness and mortality, and its formula is on its page. They answer different questions, so the numbers won’t match.
Do I need to run for Keely’s VO2 max?
Walk or run: Keely needs 3 steady ones that a watch or an app such as Strava saves to Apple Health, with your Loop on. WHOOP estimates VO2 max without a run, from your nights and activity.
Can I use my WHOOP band with Keely?
No. Keely works with the Polar Loop.
Can I bring my WHOOP history to Keely?
No. Keely starts fresh: it learns your normal over your first nights, and your first Recovery arrives after 3.
Sources
- WHOOP membership and prices: whoop.com/us/en/membership, and Membership Pricing (May 28, 2026).
- WHOOP 5.0 and MG: WHOOP’s launch announcement, May 8, 2025.
- WHOOP Age and Pace of Aging: Healthspan guide (April 21, 2026).
- VO2 max: How accurate is WHOOP VO2 max? (April 22, 2026) and Estimate your VO2 max with WHOOP (May 29, 2026).
- Strain’s scale, and that its formula isn’t published: How does WHOOP Strain work?
- Recovery’s inputs: WHOOP Recovery and WHOOP 101.
- Stress Monitor: Introducing Stress Monitor (March 29, 2023) and Get to know the Stress Monitor.
- Data export and API: How to export your data and The WHOOP Developer Platform (August 31, 2026). Strava: What’s new in 2026.
- Polar Loop price: Polar’s US store. Specifications: Polar Loop user manual.
All checked October 5, 2026. Prices and features change, so check WHOOP’s before you buy. WHOOP is a trademark of WHOOP, Inc.; Keely isn’t affiliated with or endorsed by WHOOP or Polar.
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