Inscribed Circle Calculator

The inscribed circle (incircle) is the largest circle that fits inside a triangle, tangent to all three sides. Its radius (inradius) equals the triangle area divided by the semi-perimeter.

1. 1r = Area / s
2. 2Where s = (a+b+c)/2 (semi-perimeter)
3. 3Area found via Heron's formula
4. 4Centre is at the intersection of the angle bisectors (incentre)