Smartwatch specs: battery, phones, subscriptions and health features

The battery figure a maker headlines is measured under its own test script, and the script usually lets the screen sleep between glances. Apple spells its script out: its “all-day” figure assumes 300 time checks, 90 notifications, 15 minutes of app use and a 60-minute workout over 18 hours. Turn the always-on display on, or start a GPS workout, and a different figure applies, usually printed on a different page.

So every watch here shows three: the headline, the maker’s figure with the always-on display enabled, and its figure for a GPS workout. 21 of the 53 watches have a published always-on figure. Where both are published, switching always-on on leaves a median of 39% of the headline, and as little as 25% on the Garmin Venu X1. 23 of the 44 watches with an OLED or AMOLED screen have no published always-on figure at all; their pages say so rather than guess.

4 watches use a memory-in-pixel (MIP) screen, which reflects light and stays on by design. Their headline already includes an always-on screen, which is why they have no separate always-on figure.

For anyone who tracks runs, rides or hikes, the GPS figure decides whether the watch lasts the event. Makers quote it for their standard GPS mode; 42 watches here publish one, from a few hours on the app-platform watches to 3 days on the Garmin Enduro 4.

Dual-band (multi-frequency) GPS listens on two satellite frequencies and keeps a cleaner track among tall buildings, cliffs and tree cover. 34 watches have it. It costs battery: where a maker publishes both figures, the dual-band figure is a median 85% of the standard GPS figure (23 watches).

A watch is an accessory to a phone first. 3 watches here work only with an iPhone, 6 only with Android, and 16 work fully with either. Apple sells no Android pairing, and Samsung and Google watches do not pair with an iPhone.

The quieter lock-in is inside Android. 31 watches work with any Android phone but keep some features for the maker’s own phones or limit what an iPhone can do. For the Samsung Galaxy Watch9, its maker says: “Samsung: 'Newer Samsung watches with Wear OS are not compatible with iOS.' On Android, ECG Monitor, Irregular Heart Rhythm Notification, blood pressure, sleep apnea, Energy Score and Vitals need a Samsung Galaxy phone with Samsung Health / Samsung Health Monitor (Android 13+ for several)”

41 watches here come from makers that sell a paid tier on top of the watch; the other 12 do not. None of the tiers below is needed to use the watch, but several gate features the maker advertises. The yearly prices, from the makers’ own pages:

• Google Health Premium, $119.88/year (Google, 4 watches). No watch hardware feature needs it; Premium adds Google Health Coach (Gemini-built adaptive fitness, sleep and health coaching) and most guided workout content
• Polar Fitness Program, $107.88/year (Polar, 6 watches). No watch feature requires it. Polar: 'A subscription to Fitness Program is not required to fully enjoy Polar products or the Flow service'; it adds adaptive 4-week cardio, strength and mobility plans in Polar Flow
• Withings+, $99.5/year (Withings, 3 watches). ECG recording, AFib detection and baseline health data stay free in the Withings app. Withings+ adds Cardio Check-Up (a cardiologist reviews an ECG within 24 hours), the Readiness Indicator ("Available with a Withings+ trial"), the AI Health Assistant and a nutritionist consultation.
• Apple Fitness+, $79.99/year (Apple, 3 watches). No watch feature requires it; it adds guided workout and meditation video classes that use the watch's metrics on screen
• Garmin Connect+, $69.99/year (Garmin, 16 watches). No watch feature requires it: Garmin's chart keeps activity details, health stats, performance metrics, Garmin Coach plans, courses and LiveTrack in the free app. Connect+ adds Active Intelligence AI insights, nutrition logging, a desktop performance dashboard, live activity on the phone, 3D maps and offline Garmin Trails downloads
• Zepp Aura, $69.99/year (Amazfit, 9 watches). No watch feature requires it; Amazfit sells workout and recovery data in the Zepp App with no subscription. Zepp Aura adds unlimited AI sleep-assistant chats (free users get one message a day), detailed weekly and monthly sleep reports, and the full sleep and meditation music library.

LTE models also need a carrier plan, which the carrier prices, not the watch maker.

A smartwatch stops being fully useful when its maker stops updating it. Only 4 of the 53 watches have a published update promise:

• Samsung Galaxy Watch9: 5 years. Samsung spec page (UAE store, same model): 'Security Update Period (Valid until) 31 July 2031' — security updates, about 5 years from the July 2026 launch; the US page does not list it
• Samsung Galaxy Watch Ultra2: 5 years. Samsung spec page (UAE store, same model): 'Security Update Period (Valid until) 31 July 2031' — security updates, about 5 years from launch; not on the US page
• Google Pixel Watch 5: 3 years. Google support table: software updates 'until at least' October 2029 for Pixel Watch 5 (released October 2026) — 'at least 3 years'
• Google Pixel Watch 4: 3 years. Google support table: software updates 'until at least' October 2028 for Pixel Watch 4 (released October 2025) — 'at least 3 years'

Everything else says “not published”: the maker may well keep updating it, but has not promised to.

In the US, a health feature that claims to detect a condition needs FDA clearance (a 510(k)) or a De Novo grant; features presented only for general wellness do not. That is the line this site draws. 17 watches carry at least one feature their maker or the FDA’s database lists as cleared:

• ECG app: 10 watches
• Irregular rhythm notifications: 7 watches
• Sleep apnea notifications: 3 watches
• ECG Monitor app: 3 watches
• Sleep apnea feature: 3 watches
• Hypertension notifications: 2 watches
• Loss of Pulse Detection: 2 watches
• ECG (atrial fibrillation detection): 2 watches

Heart rate, blood oxygen, stress, HRV, VO2 max, sleep scores and readiness scores are wellness estimates. They can be useful for spotting your own trends; they are not diagnoses, and no watch here is cleared for them as such.

21 watches carry full downloadable topographic maps, 9 have downloadable maps without topo detail (or only through an app), 9 follow a route line only, and 9 have no maps. Topo maps matter off-trail; for road running a route line is usually enough.

28 watches store music for phone-free runs, 9 come in an LTE version that makes calls and streams without the phone nearby, 22 pay contactlessly, and 15 have a built-in flashlight. Each is a reason to pay more only if you will use it; the “what the extra money buys” line on each watch page lists exactly which of these a pricier sibling adds.

Makers weigh watches differently, some with the band and some without, and each weight here says which. The lightest case here is the Polar Ignite 3 at 21 g; at the other end the Amazfit T-Rex Ultra 2 starts at 89.2 g (with strap). Bigger cases hold bigger batteries, which is why the same model’s battery figures often differ by size.

The ratings here are the makers’ own words: “5 ATM” (14), “10 ATM” (11), “Swim, 5 ATM” (5), “WR50” (4), and others. A depth or pressure rating is a lab test, not a promise for every use. Apple’s own footnote is typical: a 50-metre watch “may be used for shallow-water activities like swimming in a pool or ocean” but “should not be used for scuba diving, waterskiing, or other high-velocity water sports”, and “water resistance is not a permanent condition and can diminish over time.”

• Rugged outdoor watches: 12
• Fitness watches: 12
• Running watches: 10
• Multisport watches: 8
• Everyday smartwatches: 7
• Hybrid smartwatches: 4