GoKawiilFIU study finds smartwatches overestimate calories burned by up to 25%
Florida International University researchers tested the Apple Watch Series 8, Fitbit Sense 2, Samsung Galaxy Watch 5 and Garmin Forerunner 955 against a Cosmed K5 metabolic device and ECG chest strap during controlled workouts with 58 participants. All four smartwatches overstated calorie burn, with margins of error ranging from 15% to 25%, meaning a reported 200-calorie burn could really be closer to 160-174 calories. Apple Watch was the most accurate, while Samsung and Garmin overestimated more, and Fitbit had enough tracking glitches that some of its data had to be excluded.
GoKawiil's interpretation of the reporting above, not reported fact.
Millions of people rely on wearables to guide diet and exercise decisions, so consistent overestimation could undermine weight management or fitness goals built around inaccurate calorie math. The finding that errors worsen with higher body fat percentage also raises questions about whether these devices are less reliable for the users who may need accurate tracking most.
- All four tested smartwatches overestimated calories burned by 15-25% versus a lab-grade metabolic device.
- Apple Watch Series 8 had the smallest error margin, while Samsung and Garmin overestimated more heavily.
- Accuracy declined as participants' body fat percentage increased, for reasons researchers haven't yet explained.
Polar H10 Heart Rate Sensor Chest Strap — If your smartwatch is fudging calorie numbers, a chest strap gets the heart rate data much closer to the source — the study itself used ECG chest straps as its reference. The Polar H10 pairs with Bluetooth and ANT+ apps and watches, so you can keep your existing wearable and just feed it better data.
See Polar H10 Heart Rate Sensor Chest Strap on Amazon → Affiliate link — we may earn a commission on purchases, at no extra cost to you. Product picked by AI based on this article; it is not a tested recommendation.Source: cnet.com — Corin Cesaric-Epple, 2026-09-02
Published there as: “Is The Calorie Counter on Your Smartwatch Accurate? Not Really, Study Finds”
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