actually i want to build a transformer on my own. the formula for finding the primary winding of the transformer isIf its a transformer with a sinusoidal waveform supply [such as a mains transformer] - you use the most fundamental of all the transformer equations.
\(E=4.44fNAB_m\) [Volts RMS]
where
E=Applied [usually primary] rms voltage
f=frequency [Hz]
N=turns on the winding [primary] where the voltage E is applied
A=Magnetic circuit cross-sectional-area enclosed by the winding [m^2]
Bm = the maximum flux density [Tesla]
leading to
\(B_m=\frac{E}{4.44 f N A}\) [Tesla]