Complex Numbers Calculator

Add, subtract, multiply or divide two complex numbers written in the form a + bi.

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What it asks for

The formula

Cartesian form: z = a + ib   (a = real part, b = imaginary part)
Modulus: |z| = √(a² + b²)
Argument: θ = the angle from the positive real axis, fixed by the quadrant
Polar form: z = |z| (cos θ + i sin θ) = |z| eiθ

From the article Complex Numbers — Modulus, Argument and Operations.

Worked examples

a = 3, b = 4, both positive → first quadrant.
|z| = √(3² + 4²) = √(9 + 16) = √25 = 5
α = tan⁻¹(4/3) = tan⁻¹(1.3333) = 53.13°, and since it is the first quadrant, θ = 53.13°.
Polar form: z = 5 (cos 53.13° + i sin 53.13°)

Check: 5 cos 53.13° = 5 × 0.6 = 3 ✓ and 5 sin 53.13° = 5 × 0.8 = 4 ✓

Example 2 — a second-quadrant number: z = −1 + i√3
|z| = √(1 + 3) = √4 = 2
Reference angle α = tan⁻¹(√3 / 1) = 60°. The point is in the second quadrant (a negative, b positive), so θ = 180° − 60° = 120°.
Polar form: z = 2 (cos 120° + i sin 120°).

Check: 2 cos 120° = 2 × (−0.5) = −1 ✓ and 2 sin 120° = 2 × 0.8660 = 1.732 = √3 ✓. A calculator that returned −60° would have given the point 1 − i√3 — the wrong number entirely.

Worked in full in Complex Numbers — Modulus, Argument and Operations.

Learn the method

About this tool

This is one of the tools in the Chemistry Calculator Suite, a free calculator built for IIT-JAM, CSIR-NET, GATE and CUET (Chemical Science) preparation. Nothing is behind a login and no result is stored on a server — the arithmetic runs in your own browser.

The Complex Numbers calculator above is the live tool — type your values and press its button; the answer appears in the same box. The link under it opens the full suite with this tool already selected, next to the others.

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