Smartwatch Calorie Counts Often Inaccurate, Study Finds

A study from Florida International University found that popular smartwatches often misjudge workout calories, with errors increasing as body fat rises. The Apple Watch Series 8 performed best, while Garmin and Samsung overestimated, and Fitbit was erratic. Researchers tested four watches against a clinical metabolic analyzer in 58 adults during cycling. Median errors ranged from 15 to 25 percent, with Garmin overshooting by 69 calories and Samsung by 57, while Fitbit's extreme readings inflated its average bias to 128.6 calories. The calorie error grew with body-fat percentage across all brands, likely due to optical signal quality and algorithm limitations. The study only tested one cycling workout, so users should treat calorie numbers as rough estimates, not precise measurements.