User level: Level 1 (5 points)I bought Apple Watch Ultra 4 (Watch OS 27.0 - 24R364) and use Apple Watch Series 9 with the same version of WatchOS for sleep measurement. I can see any data in Readiness app on Ultra 4, should I wait for several nights or I have to use Ultra 4 for sleep measurement instead of S9 to get results?
Posted on Sep 21, 2026 1:27 AM
User level: Level 4 (1,080 points)Sep 26, 2026 10:39 AM in response to Toma007
Yes — you should use the Ultra 4 for sleep tracking if you want it to generate its own Readiness score.
Apple says the Readiness feature on the Ultra 4 requires you to wear that watch to bed for at least 7 nights to establish your baseline. The score uses overnight vitals and sleep data, along with recent activity.
So data recorded by your Series 9 may not be enough to establish the Ultra 4's Readiness baseline. I'd wear the Ultra 4 overnight for at least 7 nights, with Sleep and Overnight Vitals enabled, and then check the Readiness app again.
User level: Level 1 (5 points)Oct 3, 2026 3:07 AM in response to poonam_kumawat
Now Readiness appears on my Apple Watch Ultra 4, I tried to use my AW Series 9 for the last night and the Readiness was not calculated. If I bought an Apple Watch Series 12 and wore it at night, and the AW Ultra 4 during the day, would “Readiness” work properly? In other words, would the data and “Readiness” status be shared between both watches and the iPhone 17 Pro Max?
Originally posted at discussions.apple.com/thread/256361737