Arctan Calculator

This calculator returns the inverse tangent of a number, the angle whose tangent you entered. Give it a single value and it prints the principal value in degrees, radians, gradians and degrees-minutes-seconds; give it a y and an x and the two-argument atan2 form puts the angle in the correct quadrant; give it the two legs of a right triangle and it returns the angle between them. Tangent accepts every real number, so nothing you type is out of range, but it repeats every 180 degrees, which is why one tangent stands for infinitely many angles and the page prints that family alongside the principal one. The atan2 tab is the one to use for a direction, because plain arctan of y over x loses the signs and reports a south-west heading as a north-east one.

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Enter the tangent and get the angle back, in degrees, radians and gradians.

Any real number, positive or negative. Tangent has no bound, so nothing is mathematically out of range; the field stops at a million so the angle stays honest to six decimal places instead of reading a flat 90 degrees.
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The two-argument form. It keeps the signs of y and x, so a point below and to the left comes back in the third quadrant instead of the first.

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In a right triangle the tangent of an angle is the opposite side over the adjacent side, so two legs give you the angle.

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