Calculate Magnetic Field I have a magnet that I cannot find a data sheet for, and am trying to figure out its magnetic field. What I have done is measure the distance the magnet attracts an object of known weight, therefore finding a force for a certain distance. I can't figure out how to use this data to find the magnetic field as every equation I find needs a known charge.
Is there a way to use this data to find magnetic field, or have I fundamentally misunderstood how magnetism works?
 A: Is Hall probe what you need? 
https://en.m.wikipedia.org/wiki/Hall_effect
Other things to try
You may be able to find some conversion tables by searching for 'magnetic pull force' https://duckduckgo.com/?q=magnetic+pull+force&t=lm&ia=web. I have seen magnets being sold by their pull force, which, I guess, means the weight of iron (?) a magnet can hold against gravitational force. 
What I would do is probably put a small loop of wire on a rotating shaft, bring that rotating loop close to the magnet, and then try to deduce the magnetic field from the voltage induced in the loop. You will need an oscilloscope for this.
Another idea is to try to get your magnet to 'fight' against the electrical magnet. You could make a small electrical magnet by winding wire. Then put the electrical magnet next to your magnet and increase the current through the electrical magnet until their fields are equal and opposite. This could be tested with iron filings
If your magnet is a dipole (just two poles on opposite side). Hang your magnet on the torsion balance. Then apply a known uniform magnetic field using the electrical magnet.Deduce the dipole moment of the magnet by how much your magnet aligns with the applied field, working against the torsion balance.
