# Apple Watch Series 12 reads your heart every five seconds

Source: https://idevice.com/the-series-12-changes-a-lot-and-shows-almost-none-of-it
Published: 2026-09-12

> The Series 11 changed four things. The Series 12 changes enough that the small heart rate complication on your watch face finally shows a live number.

[Apple Watch Series 12](https://idevice.com/smart-watches/apple-watch/roadmap) reaches stores on Friday, September 18, at [$399](https://idevice.com/the-bigger-apple-watch-series-12-costs-20-more), the same price as the Series 11, which Apple has now discontinued. MacRumors published a [side-by-side of the two watches](https://www.macrumors.com/guide/apple-watch-series-11-vs-12/) that runs to more than 25 differences, a long list after a year when the Series 11 added just four changes over the Series 10. The design has not changed for a third year. The S11 chip is the first notable performance upgrade since the S9 in 2023, RAM doubles to 4GB, and Apple is calling the new sensor package the Health Sensing System.

That system reads heart rate every five seconds, sixty times more often than before. Apple’s marketing images for the Series 12 and Ultra 4 show the small round Heart Rate complication displaying a live number instead of an app icon, a change [9to5Mac spotted](https://9to5mac.com/2026/09/11/apple-watch-series-12-makes-a-big-change-to-a-small-complication-that-im-excited-about/) in the marketing material. On a Series 11 or Ultra 3 running the watchOS 27 release candidate, that same complication is still just a launcher. Fifteen minutes of charging now buys up to twelve hours of normal use, up from eight on the Series 11.

## Sources

- [MacRumors](https://www.macrumors.com/guide/apple-watch-series-11-vs-12/) (MacRumors)
- [9to5Mac](https://9to5mac.com/2026/09/11/apple-watch-series-12-makes-a-big-change-to-a-small-complication-that-im-excited-about/) (9to5Mac)