Peer-reviewed study puts Apple Watch fitness tracking to the test: Here’s the takeaway
Heart rate and step count

Apple Watches tend to have some of the best heart rate tracking among wearables. | Image by PhoneArena
Let’s start with the good news first. According to the findings, Apple Watches are highly accurate when it comes to tracking heart rate and counting steps. This is in line with our own experience with Apple Watches, including during our Apple Watch Series 10 review (Apple’s latest smartwatch).
The mean absolute percent error (MAPE) for these metrics in the meta-analysis was just 4.43% for heart rate and 8.17% for step count — both well below the 10% threshold typically used to define excellent performance in consumer wearables.
The researchers also noted that newer Apple Watch models performed better across the board. While the study doesn’t specify model-by-model results, doctoral student Ju-Pil Choe (one of the study authors) says:
Calories burned is still a weak spot

Smartwatches are still not that great at tracking calories, but that doesn’t mean you can’t use them for motivation. | Image by PhoneArena
But not all metrics scored so well. The study found that estimates of energy expenditure — aka how many calories you burn — were far less reliable. The average error rate here jumped to 27.96%, with inaccuracies present across various activities, including walking, running, cycling, and high-intensity workouts.
That puts Apple Watch roughly on par with other wearables, like the Fitbit Surge, which also struggles with calorie estimates. This shouldn’t come as a surprise, though, as it is an extremely difficult task to measure calories burned. There are all kinds of things to factor in like body weight, movement type, metabolic efficiency, and even skin tone.
The bottom line
Use the Apple Watch — or any smartwatch, for that matter — as a guide, not gospel.
The University of Mississippi study provides a helpful reality check: Apple Watches are excellent at tracking heart rate and step count but should not be relied on for precise calorie measurements.