Example:
15 nW = 2.011533e-11 horsepower (550 ft·lbf/s)
1 nW = 1.341022e-12 horsepower (550 ft·lbf/s) | 1 horsepower (550 ft·lbf/s) = 7.456999e+11 nW
Conversion Steps:
15 × (1e-9 / 745.699871582) = 2.011533e-11