Apple’s $634 million Apple Watch patent bill just got even bigger

Apple’s $634 million patent loss to medical technology company Masimo just got even worse, after a federal judge ordered Apple to pay an additional $184 million in interest on what it owes (via Bloomberg Law).

The ruling brings Apple’s bill to about $818 million, but that doesn’t include post-judgment interest that continues to accrue until the judgment is paid.

Judge James Selna rejected Apple’s argument that adding prejudgment interest would be a windfall for Masimo, citing the U.S. Supreme Court’s ruling that “interest from the time royalty payments would have been received serves only to make the patent owner whole.” In other words, Masimo is compensated for as long as it was deprived of the royalties that it theoretically would have received during the period of infringement.

However, not everything went Masimo’s way. Selna also declined Masimo’s request to calculate it at a rate of 7%, which would have brought Apple’s interest bill to $243 million. Instead, the court used Masimo’s borrowing rate, compounded annually from the start of the offense.

Masimo is also behind the separate patent dispute that led to a U.S. import ban on certain Apple Watch models and resulted in Apple disabling the blood oxygen feature on affected newly sold models. Apple introduced a redesigned version of the feature in 2025.

The dispute here concerns a Masimo pulse oximetry patent. In November 2025, a jury found that Apple Watch features, including heart rate notifications, infringed Masimo’s patent and awarded the company $634 million.

Apple later attempted to overturn or reduce the sentence, but Selna upheld the verdict in July. The patent in question expired in June 2022, so the decision related to historical Apple Watch sales and had no effect on the heart rate features of current Apple Watch models.