Wearable Insights

Smartwatches: display, battery days, and which phone it actually works with

A smartwatch is a screen on the wrist that talks to a phone. Its specification sheet is long, and the line that matters most is near the bottom: which phone. Everything above it — display, battery, sensors — is read differently depending on the answer.

What the category is

Platform watches: Apple Watch for iPhone, Wear OS (Samsung, Google, Fossil) mostly for Android, each with an app store and daily charging. Long-battery watches (Garmin, Amazfit, Huawei, Coros) with their own operating systems, a week or more per charge, and a fixed feature set. Budget watches from small brands, with a proprietary app, calling over Bluetooth, and a spec sheet written to look like the first group. A watch with a SIM is a cellular watch and needs a plan.

How to read the spec sheet

Compatibility first: iOS, Android, or both, and what “both” leaves out. A Wear OS watch does not pair with an iPhone; a budget watch pairs with either through its own app and does little with notifications on iOS. The sheet names the app, and the app’s store listing names what it does.

Display: size in inches, AMOLED or LCD (or memory-in-pixel on long-battery watches), resolution, always-on. An AMOLED with always-on is the readable, charge-nightly choice; MIP is dim indoors and lasts weeks.

Battery in days, and under what: typical use, always-on off, GPS off. A review quotes the conditions. GPS hours, where stated, are the figure that matters for a marathon.

Sensors: optical heart rate, SpO2, ECG (which needs a regulatory clearance the sheet should name), skin temperature, barometric altimeter, compass. Presence is on the sheet; accuracy is not.

GPS: built in or from the phone, and which satellite systems (GPS, GLONASS, Galileo, dual-band). “GPS” on a budget watch often means connected GPS through the phone.

Water rating: 5 ATM is swimming; IP68 is rain and a shower; “waterproof” is a word.

Calling, payments, music: Bluetooth calling through the phone, NFC payments (and which service), onboard music storage. Each is a line on the sheet and a check against the phone.

Case size and weight: 40 to 46 mm cases, 30 to 60 grams; strap width in millimetres decides which straps fit.

Who it suits

An iPhone owner: Apple Watch, or a long-battery watch that accepts fewer notifications. An Android owner: Wear OS for the app store, or Garmin and Amazfit for the battery. A runner or cyclist: a watch with built-in multi-band GPS and stated GPS hours.

Who should skip it

Anyone who wants steps and sleep and not a second screen: a fitness tracker costs less and lasts a fortnight, and a smart ring does sleep with nothing on the wrist. A parent buying for a child needs the kids’ hub, where the questions are different.

Where to start

Six of the 452 smartwatches wearables reviewed on this site, one per model, across manufacturers. Every review is written from the manufacturer’s published specifications — how, and what that leaves out.

All 452 smartwatches wearable reviews

Newest first. Consumables, accessories and parts that were once filed here are excluded.