Example:
15 Btu (th) = 3.777408 calorie (nutritional)
1 Btu (th) = 0.251827 calorie (nutritional) | 1 calorie (nutritional) = 3.970977 Btu (th)
Conversion Steps:
15 × (1054.349999974 / 4186.8) = 3.777407567