Example:
15 calorie (nutritional) = 59.524811 Btu (IT), Btu
1 calorie (nutritional) = 3.968321 Btu (IT), Btu | 1 Btu (IT), Btu = 0.251996 calorie (nutritional)
Conversion Steps:
15 × (4186.8 / 1055.05585262) = 59.52481079