# How is calorie consumption calculated in the SELFLOOPS apps?

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If you are not in a lab, caloric expenditure incurred during your physical endeavors are calculated using formulas. Different applications and devices use their own methods to estimate the calories burned during an activity.

If the device you use calculates the calories burned, we will use the values provided. Otherwise, we will calculate the calories burned using the following approach.

Caloric Estimations from Power Data

With power data, we use the following formula

kcal = kJ / 4.186 / .22

• Kilojoules (kJ) emanate from measurements derived from the trainer or power meter.
• 4.186 kJ = 1 kcal = 1 Calorie
Standard assumption of human mechanical efficiency = 22%

Caloric Estimations from Heart Rate Data

When power data is not available, heart rate data is used as alternative for caloric expenditure assessment. We use the following formula to estimate calories burned (from *Keytel et al. (2005)):

Man kcal = ((-55.0969 + (0.6309 x HR) + (0.1988 x W) + (0.2017 x A))/4.184) x 60 x T
Woman kcal = ((-20.4022 + (0.4472 x HR) – (0.1263 x W) + (0.074 x A))/4.184) x 60 x T

HR = average heart rate (in beats/minute)
W = Weight (in KG)
A = Age (in years)
T = Exercise duration time (in hours)

*Keytel, L. R., Goedecke, J. H., Noakes, T. D., Hiiloskorpi, H., Laukkanen, R., van der Merwe, L., & Lambert, E. V. (2005). Prediction of energy expenditure from heart rate monitoring during submaximal exercise. Journal of Sports Sciences, 23(3), 289–297.