copy and paste the number you got by clicking the Get Curvature button above into the 1st Number box below,
type into the 2nd Number box 12 [to tell you how many Feet], and click the Divide button

The Result is :

let me give an example:
if you use 46.22 miles in the Mile field and get the alleged curvature that is 17076.647579704444 inches
copy and paste into the 1st Number field: 17076.647579704444
then type into thw 2nd Number field: 12
and click the Divide button you get
The Result is :
1423.0539649753703
what this example of say chicago sears bldg to new buffalo shore 46.22 miles means is two people on each side of the lake michigan can see each other with telescopes - and there is no curvature of the earth obstructing their line of sight view of each other, in other words the earth, IF it is curved, should block out of sight both people from each other by 1,423 feet (over the horizon)

ok this is intended to be more accurate,,
here are the numbers i am trying to put in:
earth equator radius 3963.1676 miles,
convert 3963.1676 miles to 251106299.136 inches,
compare a 63360 inches mile line with a 63360 inches mile arc starting at the same point (12 o'clock),
and strike an arc in a clockwise manner and at the clockwise ENDPOINT of the arc draw a line to the closest ENDPOINT of the mile line,
the line which connects the endpoints is 7.99360591 inches in length not quite 8 inches

i use AutoCAD to LENGTHEN the arc using TOTAL to one mile so that AutoCAD sees the arc length not the chord,