Example:
15 calorie (nutritional) = 3.919793e+20 keV
1 calorie (nutritional) = 2.613195e+19 keV | 1 keV = 3.826733e-20 calorie (nutritional)
Conversion Steps:
15 × (4186.8 / 1.602177e-16) = 3.919793e+20