Apple explains how the Apple Watch Readiness score works

Apple says the new Readiness score is possible because the Apple Watch Series 12 and Ultra 4 use a redesigned Health Sensing System. The feature evaluates sleep score, vitals such as temperature and blood oxygen, recent workouts, and training load to indicate whether someone may be ready for a demanding day or should pace themselves.

Scores appear in the dedicated Readiness Watch app, a Watch complication, and the redesigned Health app. Apple says workout data can come from third-party apps as well as its own apps. Users need seven nights of sleep data to establish a baseline.

Apple scores Readiness from 1-10, rather than the 1-100 scale used by Oura, Google and Garmin. The company says the shorter scale supports a simple, glanceable result while allowing users to explore the data behind it.

The score relies partly on more frequent heart-rate monitoring. The Apple Watch Series 11 can measure heart rate continuously every five minutes, while the Series 12 and Ultra 4 can do so every five seconds. Apple says this difference is why only the Series 12 and Ultra 4 provide Readiness scores.

For the Series 12 and Ultra 4, Apple also introduces overall HRV and recovery HRV. Recovery HRV contributes to Readiness and can be viewed in the Watch heart app. Apple says studies, including its Heart Rate and Movement study announced in 2019 and its Heart Rate Accuracy study, helped tune and assess the feature.