Eigenvalue & Eigenvector Calculator

Free Client-Side Step-by-Step

Calculate eigenvalues and eigenvectors using the characteristic polynomial det(A−λI)=0, power iteration, or QR algorithm. Supports 2×2 to 4×4 matrices with step-by-step solutions. 100% client-side—no data sent to servers.

Matrix Input
Supports 2×2 to 4×4 matrices
One row per line, space or comma separated
Quick Presets
Eigenvalues & Eigenvectors
Enter a square matrix and click "Calculate" to find eigenvalues and eigenvectors.
Step-by-Step Solution
Detailed computation steps will appear here.
About Eigenvalues & Eigenvectors

What are Eigenvalues and Eigenvectors?
For a square matrix A, a scalar λ is an eigenvalue and vector v is an eigenvector if: A v = λ v

Characteristic Polynomial:
Eigenvalues are roots of det(A - λI) = 0, where I is the identity matrix.

For 2×2 matrices:
If A = [[a,b],[c,d]], then λ² - (a+d)λ + (ad-bc) = 0
Eigenvalues: λ = (trace ± √(trace² - 4det)) / 2

Properties:

  • Sum of eigenvalues = Trace(A)
  • Product of eigenvalues = det(A)
  • Symmetric matrices have real eigenvalues
  • Orthogonal matrices have |λ| = 1

Methods:

  • Characteristic Polynomial: Exact for 2×2, 3×3 matrices
  • Power Iteration: Finds dominant (largest) eigenvalue
  • QR Algorithm: Iterative method to find all eigenvalues

Applications:

  • Principal Component Analysis (PCA)
  • Stability analysis of differential equations
  • Google PageRank algorithm
  • Quantum mechanics and vibration analysis

Exam-Style Practice

About This Eigenvalue & Eigenvector Calculator

For a square matrix A, eigenvalues λ satisfy det(A − λI) = 0 and eigenvectors v satisfy A v = λ v. This tool uses the characteristic polynomial for 2×2, power iteration for the dominant eigenvalue, and QR algorithm for all eigenvalues. All calculations run client-side—no data stored.

Authorship & Expertise

  • Author: Anish Nath
  • Background: Math and developer tools for education
  • Method: Characteristic polynomial, power iteration, QR

Trust & Privacy

  • Privacy: All calculations run locally; no data stored
  • Client-side: Your matrices never leave your device
  • Support: @anish2good

Eigenvalues & Eigenvectors: FAQ

How do I find eigenvalues of a matrix?

Enter a square matrix and click Calculate. The tool solves det(A − λI) = 0 to get eigenvalues λ, then computes eigenvectors by solving (A − λI)v = 0 for each λ.

What if the eigenvalues are complex?

For some real matrices the characteristic polynomial has complex roots; these appear as complex conjugate pairs and the corresponding eigenvectors are complex as well.

What sizes and methods are supported?

This calculator supports 2×2 to 4×4 matrices and offers characteristic polynomial, power iteration (dominant eigenvalue), and QR algorithm to find all eigenvalues.

What is the spectral theorem and why does it matter?

The spectral theorem states that every real symmetric matrix can be diagonalized by an orthogonal matrix. This means its eigenvalues are all real and eigenvectors are orthogonal — essential for PCA, physics, and optimization.

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