The new Apple Watch Ultra is Apple’s biggest change to the Apple Watch since its original release. With a completely new design, a focus on durability and extreme sports, and multiday battery life, the Apple Watch Ultra is likely to impress when it officially launches later this month.

Ahead of that launch, new regulatory filings have revealed more Apple Watch Ultra specifications. Apple’s own product page for the Apple Watch Ultra also notes a caveat with its 36-hour claim.

Apple Watch battery capacity details

As first reported by MySmartPrice, the most notable thing revealed by these filings is additional information about the battery size. According to the regulatory filings, the Apple Watch Ultra has a battery that’s 76% bigger than the battery inside the 45mm Apple Watch Series 8 and 92% bigger than the 41mm.

This roughly lines up with Apple’s claim that the Apple Watch Ultra can last for up 36 hours on a charge, which is twice as long as the Apple Watch Series 8 can last on a charge. Here are the full details:

  • Apple Watch SE 40mm: 245 mAh
  • Apple Watch SE 44mm: 296 mAh
  • Apple Watch Series 8 41mm: 282 mAh
  • Apple Watch Series 7 41mm: 284 mAh
  • Apple Watch Series 8 45mm: 308 mAh
  • Apple Watch Series 7 45mm: 308 mAh
  • Apple Watch Ultra 49mm: 542 mAh

Apple Watch Ultra battery life with LTE

Meanwhile, there’s an interesting tidbit worth noting regarding the real-world battery life of the Apple Watch Ultra. Apple touts that you can get “up to” 36 hours of battery life from the Apple Watch Ultra. As the product features page for the Apple Watch Ultra says, however, you’ll see a significant drop in battery life while using LTE.

  • Apple Watch Series 7 41mm: 284 mAh

  • Apple Watch Series 7 45mm: 308 mAh

Apple said that Apple Watch Ultra can last for up to 18 hours on a single charge when connected to LTE:

Apple said that its claim of 36 hours of battery life is based on a total of eight hours of LTE connection and 28 hours of connection to an iPhone via Bluetooth over the course of 36 hours.

Cellular is built into every Apple Watch Ultra. With a service plan, you can keep in touch with up to 18 hours of all-day LTE battery life. It works almost anywhere with international roaming.

Every Apple Watch model has shorter battery life when it’s used purely on LTE rather than paired with a nearby iPhone via Bluetooth. Interestingly, Apple does not reveal battery life details for the Apple Watch Series 8 when it’s connected solely to LTE.

Instead, Apple says that its 18-hour claim for the Apple Watch Series 8 is based on a total of four hours of LTE connection and 14 hours of connection to an iPhone via Bluetooth over the course of 18 hours.