Tangent Calculator

About this calculator

The tangent of an angle is the ratio of the length of the side opposite it to the side adjacent to it in a right triangle, equivalently defined as sin(θ)/cos(θ) on the unit circle. Because it's a ratio of the other two trig functions, tangent is undefined wherever cosine is zero — at 90° and 270° — and it repeats with a period of 180°, unlike sine and cosine which repeat every 360°. This calculator also returns the cotangent, its reciprocal (adjacent over opposite), for the same angle.

Enter an angle in either degrees or radians and it computes both values instantly, sparing you the unit conversion and lookup-table work by hand. Students working through trigonometry homework, engineers computing slopes and grades, surveyors calculating elevation angles, and physicists resolving vector components reach for tangent constantly — it's the function that directly relates an angle to a rise-over-run slope, which is why it shows up in everything from roof pitch calculations to projectile motion problems.