Complex Conjugate Calculator

Find the complex conjugate, absolute value, and explore complex number properties

Calculate Complex Conjugate

Enter the real and imaginary parts of your complex number in the form a + bi:

Any real number

Coefficient of i

Your complex number:

z = 2 + 3i

Results

Complex Conjugate

z̄ = 2 − 3i

The imaginary part changes sign

Absolute Value (Modulus)

|z| = 3.605551

Distance from origin on complex plane

Product z × z̄
13.000000
Argument
56.31°
Quadrant
First (upper right)

Complex Plane Visualization

Original number: (2, 3)
Conjugate: (2, -3)
Relationship: The conjugate is the reflection of the original across the real axis (x-axis)
Distance from origin: Both have the same distance = 3.605551

Step-by-Step Solution

Step 1: Identify Complex Number

Start with the complex number in standard form:

z = 2 + 3i

Where a is the real part and b is the imaginary part.

Step 2: Apply Conjugation Rule

The complex conjugate changes the sign of the imaginary part:

z̄ = a - bi = 2 − 3i

The real part stays the same, only the imaginary part changes sign.

Step 3: Calculate Absolute Value

The modulus (absolute value) is calculated as:

|z| = √(a² + b²) = √(2² + 3²) = √12.999999999999998 = 3.605551

This represents the distance from the origin to the point on the complex plane.

Step 4: Verify Using Multiplication

Multiplying a complex number by its conjugate gives the square of the modulus:

z × z̄ = (2 + 3i) × (2 − 3i) = 12.999999999999998

This equals |z|² = 3.605551² = 13.000000

Complex Conjugate Properties

Double Conjugation

The conjugate of a conjugate returns the original number

(z̄)̄ = z

(2 − 3i)̄ = 2 + 3i

Geometric Interpretation

Conjugation reflects the point across the real axis

z and z̄ are mirror images across the x-axis

Original: (2, 3), Conjugate: (2, -3)

Same Modulus

A complex number and its conjugate have the same absolute value

|z| = |z̄|

|2 + 3i| = |2 − 3i| = 3.605551

Example Problems

Example 1

Number: 3 + 4i
Conjugate: 3 - 4i
|z|: √(3² + 4²) = 5
z × z̄: 9 + 16 = 25

Example 2

Number: -2 + 5i
Conjugate: -2 - 5i
|z|: √(4 + 25) = √29 ≈ 5.385
z × z̄: 4 + 25 = 29

Example 3

Number: 7 (real number)
Conjugate: 7
|z|: 7
Note: Real numbers equal their conjugates

Example 4

Number: 6i (purely imaginary)
Conjugate: -6i
|z|: 6
Note: Pure imaginary numbers just change sign

Quick Reference

Complex Number
z = a + bi
Complex Conjugate
z̄ = a - bi
Absolute Value
|z| = √(a² + b²)
Product Property
z × z̄ = |z|²

Key Properties

Double Conjugation
(z̄)̄ = z
Sum/Difference
(z₁ ± z₂)̄ = z̄₁ ± z̄₂
Product
(z₁ × z₂)̄ = z̄₁ × z̄₂
Quotient
(z₁/z₂)̄ = z̄₁/z̄₂

Complex Plane

Horizontal axis = Real part

Vertical axis = Imaginary part

Conjugate = reflection across x-axis

Distance from origin = |z|

Applications

Engineering
Signal processing, control systems
Physics
Quantum mechanics, wave functions
Mathematics
Polynomial roots, complex analysis
Computer Graphics
Rotations, transformations

Understanding Complex Conjugates

What is a Complex Conjugate?

The complex conjugate of a complex number z = a + bi is the number z̄ = a - bi. It's obtained by changing the sign of the imaginary part while keeping the real part unchanged. This simple operation has profound mathematical significance and geometric interpretation.

Geometric Meaning

On the complex plane, conjugation represents a reflection across the real axis (x-axis). If you imagine placing a mirror along the horizontal axis, the conjugate would be the reflection of the original complex number.

Why Are Conjugates Important?

  • They help convert complex division to real arithmetic
  • Essential in finding polynomial roots
  • Used in quantum mechanics and signal processing
  • Help calculate distances and magnitudes

Key Mathematical Properties

Multiplicative Property

When you multiply a complex number by its conjugate, you always get a real number:

z × z̄ = (a + bi)(a - bi) = a² + b² = |z|²

Conjugate Pairs

Complex roots of polynomials with real coefficients come in conjugate pairs:

If z is a root, then z̄ is also a root

Division Simplification

Conjugates help rationalize complex fractions:

1/z = z̄/|z|²

Real-World Applications

Electrical Engineering

AC circuit analysis, impedance calculations, and power factor corrections all rely heavily on complex conjugates.

Quantum Physics

Wave function normalization and probability calculations require complex conjugates to ensure real-valued results.

Signal Processing

Fourier transforms, filter design, and signal analysis use conjugates for frequency domain calculations.