The Circular ring continuously monitors your activity. Thanks to a movement and multiple PPG sensors, Circular correlates the data to determine your calories burned. Circular uses a principle which calories burning is strongly correlated with your heart rate and your VO2 Max. 

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While heart rate alone can offer some insight into the number of calories your burn, it can also be misleading. This is because your heart rate is not influenced solely by the intensity of your physical activity.

After large amount of investigation, we came up with a reasonably accurate estimate of calorie burned calculation that use gender, age, weight, VO2 max and Heart Rate.

The number of kcal you will see displayed in the activity analysis circle is the total daily amount of calories burned at the time you look at the app, including your core sleep period. Circular continuously tracks your calories, whether you are sleeping, exercising, walking or not moving.

The Circular ring is the most unobtrusive and fashionable solution to track your calories expenditure and vital signs at any moment of your daily life.

You can read the article about Active Calories vs Total Calories