Complex Argument Calculator
This complex argument calculator works out the argument, or phase angle, of any complex number written as a plus bi, where a is the real part and b is the imaginary part. The argument is the angle the number makes with the positive real axis when plotted on the complex plane, and together with the modulus, or distance from the origin, it forms the polar form of a complex number. Working in polar form makes multiplying, dividing and raising complex numbers to powers far simpler than in rectangular form, which is why the argument shows up in electrical engineering, signal processing, control theory and maths courses alike. To use the tool, type the real part into the first field and the imaginary part into the second. It instantly returns the argument in degrees as the headline result, plus the same angle in radians and the modulus underneath, updating live as you change the numbers. Behind the scenes it uses the two-argument arctangent function, atan2, rather than a plain arctan, so the angle always lands in the correct quadrant, even when the real part is zero. The principal value returned sits between minus 180 and 180 degrees, or minus pi and pi radians. Results are rounded for display, so treat very small argument or modulus values near zero with a little care.
The formula
The argument of a + bi is atan2(b, a), the angle from the positive real axis. Using atan2 rather than plain arctan gives the correct quadrant. It is usually taken in the range minus 180 to 180 degrees.
Worked example
For 3 + 4i, the argument is atan2(4, 3), about 53.13 degrees or 0.927295 radians, and the modulus is 5. Enter 3 and 4 to confirm.
Frequently asked questions
What is the argument of a complex number?
The angle it makes with the positive real axis on the complex plane, found with atan2 of the imaginary over the real part.
Why use atan2?
It returns the correct quadrant and works when the real part is zero, unlike plain arctan.
What range is it in?
The principal value runs from minus 180 to 180 degrees, or minus pi to pi radians.
Who this calculator is for
This calculator is for algebra students and anyone needing a quick, reliable result.
What this calculator assumes
- You enter valid numbers.
- The standard method is applied.
- Results are rounded for display.
Formula and sources
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