If you want the mathmatical answer...
Dividing the amount of lateral (or vertical) movement of the rear (or front) sight by the sight radius will equal the quotient of the distance moved on target by the distance to the target.
To determine the amount of lateral or vertical movement per click, count the number of threads per inch of the control screw. One tenth of that count means a movement of .1 inches. From there, one must divide the turns into the number of threads....
(A regular micrometer is made with 40 lines per inch on the main screw. Four turns make .100 inch. One turn is .025 inch. Then, 1/25th turn makes .001 inch.)
Or, just run the rear sight 10 clicks and measure how far the sight moved.....
I still like the shoot and measure method.
Once determined, it will remain constant... two inches at 10 yards will be 4 inches at 20 yards and 20 inches at 100 yards.
Oh... the rule for Smith and Wesson adjustable rear sights is "Right is Down and Right". Or...turning clockwise moves elevation down, and windage right.
For those raised with digital clocks.... you're on your own.