Which smartwatch to buy? Six things that matter

Which smartwatch to buy has no single answer. Someone who wants to take calls needs something different from someone who wants a long battery, and a runner needs something different from a person who only wants the time and notifications. Instead of chasing specs, weigh the six points below against your own habits. By the end you will know whether you need a full smartwatch or simply a slim fitness tracker.

1. Compatibility with your phone

Check this first. Some watches only unlock their full features with an iPhone, some only with Android, and most mainstream models work with both through their own app. Read the compatibility section on the listing, note the companion app's name and check its language support. If a watch cannot connect properly, none of its features matter.

2. Real battery life for the way you use it

Advertised battery figures are usually measured in power-saving mode. An always-on display, continuous heart-rate tracking, GPS and frequent calls all drain the battery faster. As a rule of thumb:

• AMOLED screens look great but use more power.
• Models with GPS and calling usually need charging every few days.
• Small-screen trackers can run one to two weeks.

If you hate charging, start with fitness trackers.

3. Smartwatch calls or vibration alerts only

Models with a speaker and microphone let you take calls on your wrist while your phone is nearby. Cheaper ones only vibrate, so you still need to pull out your phone. If you ride a scooter, cook or carry a child, wrist calls are genuinely handy; if you mostly read messages, vibration alerts are enough.

4. Screen, case size and water resistance

The screen should be bright enough to read outdoors. Buyer photos and videos show this far better than marketing images.

5. Health features: helpful, but not medical devices

Step counts, heart rate, sleep tracking and move reminders are great for building habits. Readings such as blood pressure or blood oxygen on a watch only show trends and do not replace medical devices or a doctor's advice. Do not buy a watch just because it claims to measure many health conditions.

6. App quality, updates and replacement bands

A good app shows your data clearly, syncs reliably and keeps getting updates. Also check whether the watch uses standard 20 or 22 mm straps or a proprietary connector: standard straps are cheaper and come in far more styles; see watch straps.

Common mistakes when buying a smartwatch online

Most disappointments are avoidable. Before you check out, run through this list:

• Skipping the compatibility notes, then finding the watch will not pair with your phone or does not show messages in your language.
• Trusting the advertised battery figure instead of reading what real buyers say about battery life.
• Choosing a case that is too large for a small wrist, which makes it uncomfortable to sleep in.
• Forgetting a screen protector or spare band, so the screen is scratched within weeks. See watch accessories.
• Expecting medical-grade readings from a fitness gadget.

Quick picks by need

• Students and first-time users: a tracker or basic smartwatch with long battery life.
• Office workers: round face, calls and notifications, leather or metal strap.
• Runners and swimmers: built-in GPS, 5 ATM or more, silicone strap.

To narrow it down now, use the watch finder or browse smartwatches ranked by an independent score.

Looking after a smartwatch so it lasts

Charge it with the dock it came with, wipe the charging contacts after workouts so sweat does not corrode them, and install software updates when the app prompts you. Avoid leaving the watch in a hot car or wearing it in a sauna, since heat shortens battery life. Rinse a silicone band in fresh water after swimming in the sea or a pool.