Sure they will. To truncated whole percents, (N2-N1)×100÷N1, using integer ops, gets you that, to whole percents rounded half up, ((N2-N1)×100+50)÷N1 does it. For additional decimal places, increase the fixed multiplier (and added factor for round-half-up) by the appropriate power of 10.
Even if you are dealing in units of hundreds of billions of dollars tracked to mils, this gets you up to, I think, a hundred-thousandth of a percent with int64.
Even if you are dealing in units of hundreds of billions of dollars tracked to mils, this gets you up to, I think, a hundred-thousandth of a percent with int64.