About activity

Take the estimates of calories burned with a grain of salt. Studies show that while Apple Watch heart rate measurements are quite reliable, usually within a 5% margin of error, estimates for energy expenditure (calories burned) are less accurate.

Research indicates that the Apple Watch’s estimates of calories burned can be within 18-40% of the true value. In more extensive evaluations, discrepancies of up to 27% have been reported. No fitness tracker achieves perfect accuracy in measuring calorie expenditure​.