Smartwatches With the Longest Battery Life

If you have an iPhone and want a watch that does everything — messages, payments, apps, calls — the Apple Watch is the best smartwatch made; it lasts a day and a half. If you run or ride seriously, a Garmin tracks more accurately over long sessions, lasts a week or two and works with either phone, and is a worse smartwatch. Most people who ask this question want the Apple Watch.

Against a chest strap on steady runs every watch here was within 2–3 bpm on average. On intervals the Apple Watch Series 10 and Garmin Forerunner 265 tracked the fastest; the Amazfit and Fitbit lagged on sharp changes. For medical-grade readings use a strap — every maker says so.

Only if you want to leave the phone at home and still take calls and stream music. It adds $50–$100 to the watch and about $10 a month to the phone plan. Runners who carry a phone anyway can skip it.

Two testers wear each watch for a week each alongside a chest strap on every run, a 5K on a measured course for GPS, and the same interval session. We log heart-rate error, GPS distance error and sleep-staging consistency, time the battery with always-on display and a daily 30-minute GPS workout, and use every smart feature with the matching phone.