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Endpoint Calculator.

Find the missing endpoint when the other endpoint and midpoint are known.

On-device calculationNo signup
01

Set your values

Results update as you type.

x2: 8

x2

8.000000
y2: 11

y2

11.000000

Results update automatically as you type.

Use Cases

Solve geometry homework problems

Quickly find the missing endpoint when given one endpoint and the midpoint, a common problem in coordinate geometry.

Example: If endpoint A is (2,3) and midpoint M is (5,7), find endpoint B.

Verify manual calculations

Check your work when solving for an endpoint in math assignments or exam prep, ensuring accuracy.

Example: Double-check your computed endpoint for a line segment with midpoint (0,0) and endpoint (-4,6).

Frequently Asked Questions

How do I use the endpoint calculator?
Enter the x and y coordinates of the known endpoint and the midpoint. The calculator will compute the coordinates of the missing endpoint using the midpoint formula.
What is the formula for finding an endpoint?
If the midpoint is (xm, ym) and the known endpoint is (x1, y1), the missing endpoint (x2, y2) is calculated as x2 = 2*xm - x1 and y2 = 2*ym - y1.
Can this calculator handle negative coordinates?
Yes, the calculator accepts negative values for the known endpoint and midpoint coordinates, and it will correctly compute the missing endpoint.

Tips & Common Mistakes

Tips

  • Ensure you enter the correct coordinates for the known endpoint and midpoint; swapping them will give a different result.
  • Remember that the midpoint is the average of the endpoints, so the missing endpoint is twice the midpoint minus the known endpoint.
  • Use the calculator to check your work on practice problems to build confidence in using the midpoint formula.
  • If you have the coordinates of both endpoints, you can verify the midpoint by averaging them.

Common Mistakes to Avoid

  • Entering the midpoint coordinates as an endpoint, or vice versa, leading to an incorrect missing endpoint.
  • Forgetting to double the midpoint coordinates before subtracting the known endpoint, resulting in a wrong answer.
  • Misreading negative signs in coordinates, especially when the midpoint or endpoint has negative values.

Last updated: August 13, 2026