Geometry

Triangle Circumcircle Calculator

Find the center and radius of the circle passing through three planar vertices.

Use consistent dimensionsArea and volume units explained below
Geometry desk
Geometry desk

Match each dimension to the shape and keep units consistent.

See the method

Set the dimensions

Runs on your device

Your measurement

Your result

Let’s calculate.

Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter vertex a x, vertex a y, vertex b x, vertex b y, vertex c x, vertex c y.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

The method, explained

Translate A to the origin and solve the perpendicular-bisector equations 2u·AB=|AB|² and 2u·AC=|AC|². Translate the center back; its distance to A is the radius.

A WORKED EXAMPLE

Using vertex a x = 0, vertex a y = 0, vertex b x = 4, vertex b y = 0, vertex c x = 0, vertex c y = 3, the result is 2.5. Change these example inputs to match your task; use the method above to check each step.

Understanding your result

Yes. An obtuse triangle has its circumcenter outside; a right triangle has it at the midpoint of the hypotenuse.

What to keep in mind

Main result is radius. Nearly collinear points are numerically sensitive; coordinates must share one unit. Use the indicated units consistently. Ideal shapes are assumed; dimensions must describe the same object. Display rounding does not increase measurement precision.

Common questions

Can the center lie outside the triangle?

Yes. An obtuse triangle has its circumcenter outside; a right triangle has it at the midpoint of the hypotenuse.

How can I check the result?

Translate A to the origin and solve the perpendicular-bisector equations 2u·AB=|AB|² and 2u·AC=|AC|². Translate the center back; its distance to A is the radius. The worked example uses editable inputs. Calculations run on your device; no external API or account is required.

Methodology maintained by ClarityKit. How these tools are built and checked.