Hi,
One of the equations sometimes called the "Transformer" equation is:
B=E*10^8/(4.44*F*A*N*S)
where
B is the flux density in Gausses,
E is the AC rms voltage in volts,
F is the frequency in Hertz,
A is the core cross sectional area in square centimeters,
N is the number of turns,
S is the stacking factor, which ranges between about 0.8 to about 0.95 depending on if the laminations are interleaved or butt stacked.
For transformers made to run off the line voltage the core material is usually Si steel which has a max B of about 20KGauss, but using a max of about 15KGauss allows for some room at the top so it does not saturate.
The core cross sectional area is measured by multiplying the width of the center leg times the stack height.
Another thing you could do is calculate the required number of turns with a lower voltage, wind the required number of turns, then aopply that lower AC voltage and check the input excitation current to see that it is not too high. You may get some buzzing too because the windings will not be varnished, and if the core is not varnished you'll get more audible buzzing.