Calorie Readouts on Apple Watch Remain Educated Guesses, Not Exact Measurements

New analysis finds Apple Watch calorie readings are educated guesses, not precise measurements: wearables can track heart rate, but energy expenditure is estimated from proxies like movement and heart rate, leading to sizable errors (Stanford 2024: average ~27% off, some devices up to 93% off); a Nature study also notes accuracy degrades with factors like multiple sensors and skin tone. Providing height and weight may improve estimates, but true calorie burn remains highly variable, so treat these numbers as estimates rather than exact facts.