📊 Matrix Multiplication Calculator

A powerful, easy-to-use online tool for multiplying matrices and calculating matrix products with step-by-step explanations. Solutions come with steps. 

🧮 Matrix Calculator

🅰️ Matrix A
Rows: Columns:
🅱️ Matrix B
Rows: Columns:
🎯 Result: A × B

📝 Step-by-Step Solution

Enter matrix dimensions and values, then click "Calculate" to see the step-by-step solution.

📚 Understanding Matrix Multiplication

What Is Matrix Multiplication?

Matrix multiplication is a binary operation that takes a pair of matrices and produces another matrix. Unlike simple arithmetic multiplication, matrix multiplication follows specific rules and has requirements on the dimensions of the matrices.

💡 Matrix multiplication is fundamental to linear algebra and has numerous applications in science, engineering, computer graphics, and data analysis.

Compatibility Rule

⚠️ Two matrices can be multiplied only when the number of columns in the first matrix equals the number of rows in the second matrix.

Compatibility Example

Matrix A (3×2)
a11 a12
a21 a22
a31 a32
×
Matrix B (2×4)
b11 b12 b13 b14
b21 b22 b23 b24
=
Result (3×4)
c11 c12 c13 c14
c21 c22 c23 c24
c31 c32 c33 c34

Columns of A (2) = Rows of B (2) ✓ Compatible

The Multiplication Process

To calculate the element at position (i, j) in the resulting matrix:

  1. Take the ith row of the first matrix
  2. Take the jth column of the second matrix
  3. Multiply corresponding elements and sum them up

🔢 Mathematically, if C = A×B, then:

C[i,j] = A[i,1]×B[1,j] + A[i,2]×B[2,j] + ... + A[i,n]×B[n,j]

Step-by-Step Example

Let's multiply these two matrices:

Matrix A (2×3)
1 2 3
4 5 6
×
Matrix B (3×2)
7 8
9 10
11 12
Element C[1,1]
Element C[1,2]
Element C[2,1]
Element C[2,2]

Calculating C[1,1]:

Take row 1 from A: [1, 2, 3]

Take column 1 from B: [7, 9, 11]

Multiply corresponding elements and sum:

C[1,1] = 1×7 + 2×9 + 3×11

C[1,1] = 7 + 18 + 33 = 58

Calculating C[1,2]:

Take row 1 from A: [1, 2, 3]

Take column 2 from B: [8, 10, 12]

Multiply corresponding elements and sum:

C[1,2] = 1×8 + 2×10 + 3×12

C[1,2] = 8 + 20 + 36 = 64

Calculating C[2,1]:

Take row 2 from A: [4, 5, 6]

Take column 1 from B: [7, 9, 11]

Multiply corresponding elements and sum:

C[2,1] = 4×7 + 5×9 + 6×11

C[2,1] = 28 + 45 + 66 = 139

Calculating C[2,2]:

Take row 2 from A: [4, 5, 6]

Take column 2 from B: [8, 10, 12]

Multiply corresponding elements and sum:

C[2,2] = 4×8 + 5×10 + 6×12

C[2,2] = 32 + 50 + 72 = 154

Final result:

58 64
139 154
Special Cases and Properties
🔄 Identity Matrix

The identity matrix (I) has 1s on the main diagonal and 0s elsewhere. When a matrix is multiplied by the identity matrix of appropriate size, the original matrix is unchanged.

A × I = I × A = A

Example: 3×3 Identity Matrix

5 2 8
1 3 7
4 6 9
×
1 0 0
0 1 0
0 0 1
=
5 2 8
1 3 7
4 6 9

The original matrix remains unchanged when multiplied by the identity matrix.

⚠️ Order Matters

Matrix multiplication is not commutative. In general:

A × B ≠ B × A

Non-Commutativity Example

A × B:

1 2
3 4
×
5 6
7 8
=
19 22
43 50

B × A:

5 6
7 8
×
1 2
3 4
=
23 34
31 46

As you can see, A×B ≠ B×A

🔄 Other Properties

Scalar Multiplication

When multiplying a matrix by a scalar (a single number), multiply each element of the matrix by that scalar.

Example: 3 × Matrix

3 ×
2 4
1 3
=
6 12
3 9

Transpose Property

The transpose of a product is the product of the transposes in reverse order:

(A × B)ᵀ = Bᵀ × Aᵀ

Where Aᵀ means the transpose of A (rows become columns, columns become rows).

Applications of Matrix Multiplication

Matrix multiplication is used across numerous fields:

🖥️
Computer Graphics

3D transformations (rotation, scaling, translation) are represented as matrix operations. Games and animation rely heavily on matrix multiplication.

🧠
Machine Learning

Neural networks use matrix multiplication for both forward and backward propagation. Weight matrices transform input data.

🔒
Cryptography

Matrix operations are used in encryption algorithms like Hill cipher. Secret keys are often represented as matrices.

📊
Economics

Input-output models use matrices to analyze relationships between different sectors of an economy.

🌐
Network Analysis

Adjacency matrices representing networks can be multiplied to find paths between nodes. PageRank algorithm uses matrix operations.

🔬
Quantum Mechanics

Quantum states and operators are represented as matrices. Their multiplication describes how systems evolve.

🏙️
Structural Engineering

Stiffness matrices are used in finite element analysis to model how structures respond to forces.

📱
Image Processing

Convolution operations in image filters (blurring, edge detection) are implemented as matrix multiplications.

🔍 How to Use This Matrix Multiplication Calculator

Setting Up Matrices
  1. Enter the number of rows and columns for Matrix A
  2. Click "Update" to generate the input grid
  3. Enter the number of rows and columns for Matrix B
  4. Click "Update" to generate the input grid
  5. Fill in the values for each matrix cell

💡 Remember: For matrix multiplication to work, the number of columns in Matrix A must equal the number of rows in Matrix B.

This matrix multiplier calculator follows the standard rules for multiplying matrices. If you need to calculate a matrix product for matrices of different sizes, make sure they are compatible for multiplication.

Inputting Values

You can input:

  • Integers: 1, 2, 3, etc.
  • Decimals: 1.5, 2.75, etc.
  • Fractions: 1/2, 3/4, etc.

⌨️ Pro Tip: You can use the Tab key to quickly navigate between matrix cells when entering values.

Need random values? Click the "Random Values" button to populate both matrices with random numbers between 1 and 10.

Calculating and Interpreting Results

After entering your matrices:

  1. Click the "Calculate A × B" button
  2. The result matrix will appear in the result section
  3. Review the step-by-step explanation to understand how each element was calculated

🔄 Want to start over? Click the "Clear" button to reset all matrix values.

❓ Frequently Asked Questions

Why can't I multiply matrices of any size?

Matrix multiplication requires that the number of columns in the first matrix equals the number of rows in the second matrix. This is because each element in the result is calculated by taking the dot product of a row from the first matrix and a column from the second matrix, which requires them to be the same length.

What is the difference between matrix multiplication and element-wise multiplication?

Matrix multiplication follows specific rules as explained in this calculator, resulting in a matrix where each element is the sum of products of corresponding row and column elements.

Element-wise multiplication (sometimes called the Hadamard product) simply multiplies corresponding elements directly. For element-wise multiplication, both matrices must be the same size, and the result will also be that size.

Element-wise multiplication example:

1 2
3 4
5 6
7 8
=
5 12
21 32
Why is matrix multiplication not commutative?

Unlike regular number multiplication where a×b = b×a, matrix multiplication is not commutative because the operation depends on the specific arrangement of elements in the matrices. The dimensions and internal structure of matrices make A×B and B×A different operations that generally yield different results.

In some special cases (like when multiplying by an identity matrix), matrix multiplication can be commutative, but this is the exception rather than the rule.

What's the computational complexity of matrix multiplication?

The standard algorithm for multiplying an m×n matrix by an n×p matrix has a time complexity of O(m×n×p). For square matrices of size n×n, this becomes O(n³).

However, there are more efficient algorithms for large matrices:

  • Strassen's algorithm: O(n^2.807)
  • Coppersmith–Winograd algorithm: O(n^2.376)

For practical purposes with small to medium-sized matrices (like those in this calculator), the standard algorithm is usually sufficient.

Can I use this calculator for solving systems of linear equations?

While this calculator specifically focuses on matrix multiplication, solving systems of linear equations typically involves multiple matrix operations including:

  1. Representing the system as a matrix equation Ax = b
  2. Finding the inverse of A (if it exists)
  3. Computing x = A⁻¹b

For a full solution to systems of linear equations, you would need additional operations like matrix inversion or Gaussian elimination.