Formula Energy of the Magnetic Field of a Coil Magnetic energy Electric current Inductance
$$W_{\text m} ~=~ \frac{1}{2} \, L \, I^2$$ $$W_{\text m} ~=~ \frac{1}{2} \, L \, I^2$$ $$I ~=~ \sqrt{ \frac{2W_{\text m}}{L} }$$ $$L ~=~ \frac{ 2 W_{\text m} }{ I^2 }$$
Magnetic energy
$$ W_{\text m} $$ Unit $$ \mathrm{J} $$ Magnetic energy stored in the B-field of the coil.
Electric current
$$ I $$ Unit $$ \mathrm{A} $$ Electric current flowing through the coil. The larger the current, the more magnetic energy is stored in the B-field.
Inductance
$$ L $$ Unit $$ \mathrm{H} $$ Inductance (here self-inductance) is a characteristic quantity of a coil and indicates how good the coil can form a magnetic field when a current flows through it. The larger the inductance of the coil, the larger the stored energy in the magnetic field.