Tangent of a Circle Calculator
Find the tangent length from an external point to a circle.
From a point outside a circle, the tangent line touches the circle at one point. This finds its length.
The math behind it
The radius to the point of tangency is perpendicular to the tangent, forming a right triangle: tangent = √(d² − r²).
Worked example
Radius 5, distance 13 → tangent √(169 − 25) = 12.
FAQ
What if the point is inside the circle?
No tangent exists — the distance must be at least the radius.