The formula to calculate % current efficiency

$\frac{\text{Ammeter\hspace{0.17em}current}}{\text{Actual\hspace{0.17em}current}}\times 100$

$\frac{\text{Actual\hspace{0.17em}current}}{\text{Actual voltage}}\times 100$

$\frac{\text{Actual\hspace{0.17em}current}}{\text{Ammeter\hspace{0.17em}current}}\times 100$

$\frac{\text{Actual\hspace{0.17em}current}}{\text{Ammeter\hspace{0.17em}current}}\times \frac{1}{100}$