Adjoint Matrix Calculator

Adjoint Matrix Calculator

Calculate the adjoint (adjugate) matrix and determinant for 2×2 and 3×3 matrices.

2026-05-12T10:30:55.056Z

Input Matrix

Adjoint Matrix

4
-2
-3
1

Determinant

-2

What is an Adjoint Matrix?

The adjoint matrix, also called the adjugate matrix, is the transpose of the cofactor matrix. It is used in linear algebra, especially when computing inverses of square matrices.

For an invertible matrix A, the inverse can be written as A⁻¹ = (1 / det(A)) × adj(A). If the determinant is zero, the adjoint still exists, but the inverse does not.

Adjoint matrices appear in solving systems of equations, symbolic matrix algebra, control systems, and other engineering and physics applications.

How to Calculate the Adjoint

Step-by-Step Process (2×2 Matrix)

  1. 1.For a 2×2 matrix [[a, b], [c, d]], swap the diagonal elements a and d.
  2. 2.Negate the off-diagonal elements b and c.
  3. 3.The adjoint is [[d, -b], [-c, a]].

For 3×3 Matrices

  1. 1.Compute each minor determinant.
  2. 2.Apply the checkerboard cofactor sign pattern: + − + / − + − / + − +.
  3. 3.Transpose the cofactor matrix to obtain the adjoint.

Worked Example

Problem: Find the adjoint of the matrix [[1, 2], [3, 4]]

Given:Matrix A = [[1, 2], [3, 4]]
Step 1:Swap the diagonal values 1 and 4.
Step 2:Negate the off-diagonal values 2 and 3.
Step 3:det(A) = (1)(4) − (2)(3) = 4 − 6 = −2.
Answer:adj(A) = [[4, -2], [-3, 1]], det(A) = -2

Frequently Asked Questions

What is the difference between adjoint and transpose?

A transpose flips a matrix across its diagonal. The adjoint is the transpose of the cofactor matrix.

Why is the adjoint important?

It is used in the inverse formula A⁻¹ = (1 / det(A)) × adj(A) when the determinant is nonzero.

What if the determinant is zero?

The matrix is singular, so it has no inverse, but its adjoint still exists.

Can I find the adjoint of larger matrices?

Yes, but the arithmetic becomes more tedious. This calculator is limited to 2×2 and 3×3 matrices.

What is a cofactor?

A cofactor is a signed minor. You remove one row and one column, compute the minor determinant, then apply the sign pattern.

Is adjoint the same as adjugate?

Yes. In modern linear algebra, “adjoint” here means the adjugate matrix.

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