Judge Adds $184 Million in Interest to Apple's Masimo Patent Bill, Pushing Total Past $818 Million

Apple’s Masimo problem just got $184 million more expensive. This morning, U.S. District Judge James Selna ordered Apple to pay prejudgment interest on top of the $634 million a jury awarded Masimo last November for patent infringement in the Apple Watch’s heart-rate features — pushing the running total past $818 million, with post-judgment interest now accruing on top until Apple actually writes the check. MacRumors reported the ruling, citing Bloomberg Law.

Read that number again: $818 million. For a patent that expired in 2022, on heart-rate notifications. This is what happens when patent litigation meets the calendar — every month the check doesn’t get cut, the number grows. And Apple’s lawyers knew it. They fought the interest award anyway, arguing it would be a “windfall” for Masimo. Selna wasn’t having it.

The math, and why Apple’s argument failed

The judge’s order is a master class in splitting the difference. Masimo asked for interest at a 7% rate — which would have added $243 million to the bill. Apple argued for essentially nothing extra, calling any award a windfall. Selna landed in the middle: $184 million, calculated using Masimo’s own borrowing rate, compounded annually from when the infringement began.

That borrowing-rate choice is the telling part. Selna’s reasoning, as MacRumors reported, leaned on U.S. Supreme Court guidance holding, according to MacRumors, that prejudgment interest “merely serves to make the patent owner whole” from when the royalty payments would have been received. In plain English: if Apple had licensed the technology properly in the first place, Masimo would have had that money years ago — and the money it didn’t have forced it to borrow. Interest isn’t a bonus. It’s the cost of Apple holding Masimo’s money all this time.

Apple’s “windfall” framing never really had a chance against that logic. The jury already decided the infringement happened. Once that’s settled, the question isn’t whether Masimo gets paid — it’s whether Apple gets a discount for paying late. Selna’s answer: no.

This verdict was already bulletproof

This morning’s ruling is really the second act of a fight Apple has already lost twice. Back in July, Selna upheld the jury’s verdict after Apple tried to get it overturned — the standard post-trial Hail Mary, denied. Today’s order just prices the delay. With post-judgment interest now running, the meter is still moving: every month Apple spends on appeals is another month of interest compounding against it. That’s not a bug in the system. It’s the system working exactly as designed — dragging your feet on a judgment you owe makes the judgment bigger.

Worth noting, for anyone shopping for a watch today: none of this touches the device on your wrist. The patent expired in June 2022, so the ruling covers historical Apple Watch sales only. The heart-rate features in current models are completely unaffected — this is about money changing hands for past sales, not about your watch losing features.

The other war Apple is still fighting

What makes this case genuinely unusual is that Masimo isn’t just winning in the courtroom — it’s been winning at the border. The medical-tech company is behind the separate dispute that led to a U.S. import ban on certain Apple Watch models, which forced Apple to disable blood-oxygen functionality on affected newly sold models. Apple later shipped a redesigned version of the feature in 2025. That’s the part of this saga that actually reached consumers: for a stretch, if you bought a new Apple Watch in America, the blood-oxygen app wasn’t there.

Zoom out and you see the pattern. Apple is simultaneously rethinking who runs its hardware design — our report on John Ternus’s expanding design role — while paying nine-figure sums for the sins of its old sensor strategy. The company that prides itself on owning the whole stack keeps discovering that the stack has owners. And those owners, lately, are getting paid in full — with interest.

The honest read: $818 million is real money even for Apple, but it’s not the number that matters. What matters is the message every judge in every patent case just heard: argue “windfall” all you want — if the jury says you infringed, the interest clock started years ago, and it’s still ticking.

What $184 million in interest really means

Strip out the legalese and the interest award tells a simple story about time. Masimo won its patent case on the merits in November 2025. The money was owed. Every month between the infringement and the check, Apple held cash that belonged to Masimo — and Masimo, a far smaller company, had to borrow to keep its own lights on and its own R&D moving. Selna pricing the interest off Masimo’s borrowing rate is the court saying: that asymmetry has a price, and the price is yours.

There’s a reason patent lawyers watch interest fights this closely. Verdicts make headlines; interest math makes precedent. The next company weighing whether to license or litigate just got a very expensive data point: fight for five years, lose, and the “penalty” isn’t just the damages — it’s damages plus the full cost of having kept someone else’s money the whole time. That’s the sentence inside today’s sentence.