If you want them flush, you'll have to measure.
It isn't too difficult, just measure from the rotor hat (the flat area between the lug studs) out to the vertical plane that is even with the wherever you want the wheel edge to be even with. Usually this is the inside edge of the fender, as you want the wheel and tire to go up into the wheel well under compression, not into the fender. Take this measurement and subtract .75", this is your front spacing. Subtract that from your width, 9", to get your backspacing. If you need offset (which is nothing more then another expression of front/backspacing), subtract your backspacing from half your width, then convert to millimeters; this result can be negative, but only should be so if your backspacing is less then half the width of the wheel. In other words, if the front spacing is larger then your backspacing, the offset should be negative. If backspacing is larger, the offset should be positive.
Be careful with the thinking that a taller tire will "increase" the look of the drop, because a taller tire will fill the wheel well out more, but it will also lift the entire vehicle higher off the ground.
