The gap between an everyday smartwatch and an endurance tool is getting narrower. The Apple Watch Series 12 and Apple Watch Ultra 4 share Apple’s new Health Sensing System and S11 chip, making materials, battery life, and terrain the defining differences rather than core health capability.

Larger, more efficient LEDs enable heart-rate readings every five seconds throughout the day, while heart-rate variability is measured up to 24 times more often. A new readiness feature combines recent activity, training load, vitals, and sleep score into a 0-to-10 assessment that updates as new data arrives. Both watches also gain daytime vitals and more accurate step tracking, a deeper health shift than the connectivity-focused updates in Apple’s 2025 watch lineup.

Series 12 comes in 42mm and 46mm sizes, with aluminum, titanium, and pearl white or night blue ceramic cases. It retains 24-hour everyday battery life, extends outdoor workout tracking to 10 hours, and gains up to 12 hours of use from a 15-minute charge.

Ultra 4 keeps its natural or black titanium shell but stretches everyday battery life to 50 hours and Low Power Mode to 84 hours. Its Max Extended Workout mode can log outdoor runs, walks, and hikes for up to 45 hours while retaining one-second GPS readings. Both are available to preorder now and arrive September 18. Series 12 starts at $399; Ultra 4 remains $799.