The midpoint of a line is found by adding up either the "x" coordinates or the "y" coordinates, then dividing them by two. A midpoint is halfway between two end points on a line.
The formula is M = [(xa + xb)/2,(ya + yb)/2]. This formula works on all line segments, including vertical, horizontal or diagonal. The midpoint formula calculates the average, or mean, of the "x" coordinates, as well as the average or mean of the "y" coordinates.
The midpoint of the diameter of a circle is also the center of the circle. Midpoints are used primarily in the subject area of geometry.