Find the missing endpoint of a segment when one endpoint and the midpoint are known.
Last updated: June 2026 | By Patchworkr Team
Enter the known endpoint and midpoint as real numbers.
If you know one endpoint and the midpoint, the other endpoint is determined uniquely.
The formula is just the midpoint equation solved for the unknown point.
1. Enter the known endpoint.
2. Enter the midpoint.
3. Read the other endpoint from the live result panel.
If the known endpoint is (1, 2) and the midpoint is (4, 5):
x2 = 2*4 - 1 = 7
y2 = 2*5 - 2 = 8
The missing endpoint is (7, 8).
Yes. One endpoint and the midpoint determine the other endpoint exactly.
Yes. The algebra works for any real coordinates.
Yes, solve z2 = 2*mz - z1 as well.
Then the other endpoint is the same point.
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