Female: ((-20.4022 + (0.4472 x HR) - (0.1263 x W) + (0.074 x A))/4.184) x 60 x T
Male: ((-55.0969 + (0.6309 x HR) + (0.1988 x W) + (0.2017 x A))/4.184) x 60 x T
where
A is Age (in years), W is Weight (in kilograms), HR is Heart rate (in beats/minute), T = Exercise duration time (in hours)