Calculating the inductance of a coil
B = Φ / A --------------{1}

Φ = Magnetic Flux

A = Area of cross section of the coil.

B = Flux Density

Φ = (Ni) / R -----------{2}

R = Reluctance offered by the core material

N = Number of turns of coil

R = (l) / (μA) ----------{3}

μ = Permeability of the core.

l = Length of the core

A = Area of cross section of the core.

Mostly Area of cross section of core = Area of cross section of coil.


λ = NΦ = Li -----------{4}

L = λ / i


So from {2} we get,

L = NΦ / i 

L = N(Ni) / R

Hence L = (N2μA) / (l) 

So we need to know the values of  N, l, A, μ  to find the value of inductance offered by the coil.