How to calculate toroidal transformer core

The toroidal transformer iron core core cross-section, the unit is C square meters; turns per volt with the core cross-sectional area and permeability,

The relationship: N = (450 × 100000) ÷ (Bg × S), S = a × b × h. (Bg = silicon steel sheet permeability, S = core cross-sectional area, a = length, b = width, h = height).

(Bg=silicon steel sheet permeability, S=core cross-sectional area, a=length, b=width, h=height).

E.g. Outer diameter (12cm-6cm)/2 = 3cm; multiply by height.