Arctan Calculator

Mode:

atan(v) atan2(y, x)

v (ratio = opposite / adjacent)

Use when you already have the slope (y/x) or a pure ratio.

Emphasize unit:

Arctan – Quick Cheat Sheet

atan(v) returns an angle θ such that tan(θ)=v, with θ in (−90°, 90°).
atan2(y, x) returns the angle of vector (x, y) relative to +x axis, in (−180°, 180°], handling quadrants & x=0.
Units: degrees (°), radians (rad), grads (g). Conversions: deg = rad·180/π, grad = rad·200/π.
Normalization: 0–360° = (deg % 360 + 360) % 360; −180–180° re-centers around 0.
Triangles: If opposite = y and adjacent = x, then slope v=y/x. Use atan2 for correct quadrant.
Undefined cases: atan2(0,0) is undefined; if x=0, slope is infinite (vertical line).

Examples & tips

atan(1) = 45°, atan(√3) = 60°, atan(0) = 0°.
atan2(3, 4) ≈ 36.87°; atan2(-3, -4) ≈ -143.13° (or 216.87° in 0–360).
Prefer atan2 with signed y and x when direction/quadrant matters (navigation, vectors, graphics).