Apple names four inputs for the Readiness score on Apple Watch Series 12 and Apple Watch Ultra 4: recent activity, training load, vitals and sleep. Both watches measure a good deal more than that, and Apple does not say whether any of the rest reaches the score.
That is not a criticism of the four, it is a boundary worth drawing. Blood oxygen, wrist temperature, an electrical heart sensor, hypertension notifications, sleep apnea notifications, VO2 max and Health Age are all published Apple Watch measurements, and none of them appears on Apple’s Readiness input list.
Key facts
| Readiness, as published | Detail |
|---|---|
| Score | 0 to 10, once a day, updating during the day |
| Recommendations | Recover, Pace Yourself, Ready, Go For It |
| Inputs named by Apple | Recent activity, training load, vitals, sleep |
| Number of named inputs | Four |
| Weighting between the four | Not published |
| Only published comparison rule | Overnight vitals compare Recovery HRV with your personal baseline |
| Whether other measurements contribute | Not published either way |
The four Apple names, in Apple’s own order
Apple’s description is a single list: recent activity, training load, vitals and sleep. It does not rank them, it does not weight them, and it does not say how far back “recent” reaches for any of them.
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Vitals is the one category with a published rule underneath it. Apple says overnight vitals compare Recovery HRV, one of the two HRV variants it now reports, against your personal baseline. For overall HRV, the second variant, Apple publishes no comparison rule at all, and it has never said how many nights of wear the baseline is built from.
Seven published measurements that are not on the list
Each of the following is something Apple states these watches do. None is named as a Readiness input, and Apple has not said whether any of them feeds the score indirectly through the vitals category.
| Measurement or feature | What Apple publishes about it | Named as a Readiness input |
|---|---|---|
| Blood oxygen | Blood Oxygen sensor and app on Series 12 and Ultra 4 | No |
| Wrist temperature | Temperature sensor, used in Cycle Tracking | No |
| ECG | Third-generation electrical heart sensor and ECG app, ages 22 and over | No |
| Hypertension notifications | Listed on both watches, excludes several groups | No |
| Sleep apnea notifications | Listed on both watches, ages 18 and over | No |
| VO2 max | Measured by the new movement evaluations, using Apple Watch, AirPods Pro 3 or a third-party heart rate device | No |
| Health Age | Built from VO2 max, resting heart rate, sleep and HRV; requires Apple Watch | No |
Two of those, VO2 max and Health Age, live in the redesigned Health app rather than on the watch, and that app is dated only later this year, starting in US English, on devices that support Apple Intelligence. Readiness itself arrives with watchOS 27 on Monday, September 14.
What the boundary is good for
Knowing which measurements Apple has and has not tied to Readiness is the difference between reading the score as what Apple describes and reading it as a summary of everything the watch knows about you. Apple has described the first and has not claimed the second.
It is also why the score should not be read as a verdict on health. Apple claims no regulatory clearance for Readiness in any of its September 9 materials, publishes no accuracy figure for it, and labels the Vitals app as being for wellness purposes only and not for medical use. A number on a 0 to 10 scale is not a diagnosis.
What Apple has not said
- Whether blood oxygen, wrist temperature or any electrical heart sensor reading contributes to Readiness.
- Which specific measurements sit inside the vitals input.
- How recent activity, training load, vitals and sleep are weighted.
- How far back “recent activity” and “training load” reach.
- How many nights build the personal baseline behind Recovery HRV.
- Any comparison rule for overall HRV, as opposed to Recovery HRV.
watchOS 27 arrives free on Monday, September 14, and Series 12 and Ultra 4 reach stores on Friday, September 18, which is when Apple usually publishes the per-feature support documents that would define these inputs. Our event recap and Series 12 preview cover the rest of what Apple announced.
