The voltage induced across the secondary coil (out put) may be calculated from Faradays law of Induction which states that:
s is the instantaneous voltage, N
s is the number of turns in the secondary coil and Φ is the magnetic flux through one turn of the coil.
That's all you need to know, have at it.
There are other considerations to take into account; Leakage flux, leakage inductance, effect of frequency, winding resistance, hysteresis losses,eddy currents, magnetostriction,mechanical losses, various and sundry stray losses, and other problems such as electrocution.
You'll need several hundred feet of wire and some flat iron rings, the size of wire, number of turns, and number of rings can be determined from Mr Faraday's formula.
Measure twice, cut once.
Look at the nail, not the hammer. Watch the fence, not the blade.
If you hook your thumb over your belt you won't hit it with the hammer or leave it layin on the saw table.