About this tool
The Midpoint Calculator finds the exact center of a line segment from its two endpoints, in either two or three dimensions. It also reports the segment length and can work backwards to recover a missing endpoint when you already know the midpoint. All arithmetic runs live in your browser.
The midpoint is simply the average of the coordinates: M = ((x1 + x2) / 2, (y1 + y2) / 2) in 2D, with a third term (z1 + z2) / 2 added in 3D. The segment length is the straight-line distance between the two points, √((x2 − x1)² + (y2 − y1)²) with the z term in 3D. When you switch to 'Find an endpoint' mode, the tool uses the reverse identity: if M is the midpoint and P is one endpoint, the other endpoint is 2M − P, applied to each coordinate.
The result also shows the per-axis differences (Δx, Δy and Δz), which are handy for slope, direction and vector work. Because it is a pure formula, results are exact for whatever precision you type in — no rounding beyond display formatting.