Example:
15 Btu (IT), Btu = 9.877711e+22 eV
1 Btu (IT), Btu = 6.585141e+21 eV | 1 eV = 1.51857e-22 Btu (IT), Btu
Conversion Steps:
15 × (1055.05585262 / 1.602177e-19) = 9.877711e+22