About the Midpoint Calculator
The midpoint of a line segment is the point exactly halfway between its two ends. If you know the coordinates of both ends, you add the x values and halve them, then do the same for the y values. This calculator does that for any two points on a flat x-y grid, and it adds the length of the segment, the slope of the line and the angle it makes with the x-axis. It also works backwards: give it one endpoint and the midpoint, and it finds the other endpoint, which is a favourite question in geometry homework.
Updated October 2026
How to use the Midpoint Calculator
- 1Choose whether you want a midpoint or a missing endpoint.
- 2For a midpoint, type the x and y values of point A and point B.
- 3For a missing endpoint, type the known endpoint and the midpoint instead.
- 4Read the answer as a coordinate pair, with the distance, slope and angle below it.
- 5Use the copy button to paste the result into your notes.
A worked example
Take point A at (−4, 6) and point B at (10, −2). The x values add up to 6, and half of that is 3. The y values add up to 4, and half of that is 2. The midpoint is (3, 2). The run is 14, the rise is −8, so the slope is −8 ÷ 14, about −0.571, and the length is the square root of 14 squared plus 8 squared, about 16.12.
Common uses
- Finding the centre of a circle when you know both ends of a diameter.
- Locating the perpendicular bisector of a segment, which passes through the midpoint.
- Placing a label halfway along a line in a drawing or chart.
- Checking that a point splits a segment into two equal parts.
Tips for accurate answers
Keep both points in the same units and the same coordinate system. If your numbers come from a map or screen, remember that screen y values often grow downwards, which flips the sign of the slope and angle.
Related tools on this site include the Slope Calculator, the Pythagorean Theorem Calculator and the Triangle Calculator for the next step in a geometry problem.
Features
- Midpoint of any two points
- Missing endpoint from one end and the midpoint
- Distance, slope and angle of the line
- Negative numbers and decimals allowed
- Spots vertical lines and identical points
- Runs on your device
Frequently asked questions
What is the midpoint formula?
The midpoint of (x1, y1) and (x2, y2) is ((x1 + x2) / 2, (y1 + y2) / 2). It is simply the average of the two x values and the average of the two y values. For (2, 3) and (8, 11) the midpoint is (5, 7).
How do I find a missing endpoint?
Double the midpoint coordinates and subtract the known endpoint. If one end is (2, 3) and the midpoint is (5, 7), the other end is (2 × 5 − 2, 2 × 7 − 3), which is (8, 11). The calculator does this when you choose the endpoint mode.
How is the distance between two points found?
Use the distance formula, which comes from Pythagoras: take the square root of the squared difference in x plus the squared difference in y. The points (0, 0) and (3, 4) are 5 units apart.
Why does the slope say not defined?
When both points share the same x value the line is vertical, and dividing by a run of zero is not possible. The calculator then reports the slope as not defined. If the two points are identical there is no line at all.
Can I use it in three dimensions?
This version works on a flat grid with x and y. In three dimensions the idea is the same: average each of the three coordinates. For a quick 3D midpoint, calculate x, y and z separately with the same tool.
What is a midpoint used for?
Geometry class, drawing and design layouts, mapping the halfway point between two places on a grid, centring objects in graphics software and finding the centre of a circle from the ends of its diameter.