Use this triangle inradius calculator to calculate triangle inradius from the triangle sides. Learn the triangle incircle radius formula in practice.
r = inradius of triangle
a, b, c = sides of triangle
s = semiperimeter = (a + b + c)/2
The triangle incircle radius formula computes the inradius using the semiperimeter and sides.
| a | b | c | Inradius r |
|---|---|---|---|
| 3 | 4 | 5 | 1.000000 |
| 5 | 5 | 6 | 2.000000 |
| 6 | 8 | 10 | 2.400000 |
| 7 | 10 | 12 | 3.000000 |
| 8 | 15 | 17 | 5.000000 |
To manually calculate triangle inradius:
1. Compute the semiperimeter s = (a + b + c)/2.
2. Compute r = √((s − a)(s − b)(s − c)/s).
3. The result is the inradius of the triangle.
This triangle inradius calculator instantly computes the inradius using the triangle incircle radius formula with six-decimal precision.
• The incenter is the intersection point of the angle bisectors.
• The inradius is the radius of the circle inscribed in the triangle.
• All triangles have a unique incircle.
• Inradius is used in geometry, engineering, and design.
• The area of a triangle can also be calculated as A = r × s.