How to use this tangent calculator
- Type an angle into the main field — a plain number such as 45, an expression such as 30+15, or a multiple of π such as 0.25π (the π button inserts the symbol).
- Pick the unit next to the field: ° for degrees (45° gives tan = 1) or rad for radians (0.25π rad gives tan = 1).
- Press Calculate. The result is tan(x) rounded to 8 decimal places, exactly the way the classic tan(x) calculator pages compute it.
- For unit-tagged expressions, use the tangent expression box: type tan(45 deg) or tan(1 rad) and press Calculate.
- To go backwards, enter any value in the inverse tangent calculator — arctan accepts every real number — and read the angle back in degrees, radians, and as a multiple of π (e.g. arctan(1) = 45° = 0.78539816 rad = 0.25π).
The tangent of an angle is the ratio sin(x)/cos(x) — the slope of the line through the origin and the corresponding point on the unit circle — so tan(0°) = 0, tan(45°) = 1, and tan(60°) ≈ 1.73205081. The tangent repeats every 180° (π radians), and it is undefined wherever cos(x) = 0: at 90°, 270° and every other odd multiple of 90°, which is why the reference table prints “not defined” there and values grow without bound as you approach those angles. Inverse tangent goes the other way: it accepts any real number and returns the unique angle between -90° and 90°. Degrees and radians convert by the usual factor — an angle in degrees is multiplied by π/180 before the tangent is taken.
Every calculation runs locally in your browser — nothing is uploaded, and no account or connection is involved. More math tools are in Math & Statistics.