Matrix Multiplication Calculator
To multiply matrices, each entry of the product is a row of the first matrix times a column of the second; an m×n matrix times an n×p matrix gives an m×p matrix.
At a glance
| What it is | Multiply matrices online and see the row-times-column rule. Works for any sizes that match (m×n times n×p). Exact fractions. Free. |
|---|---|
| Type | Interactive guide with a calculator |
| Level | High school and college |
| Price | Free, with no account or sign-up |
| Works offline | Yes, after the first visit; installs as an app |
| Made by | Aalok (aalok.builds@gmail.com) |
| Last updated | 1 November 2026 |
Key facts
| Size rule | (m×n)·(n×p) = m×p; inner sizes must match |
|---|---|
| Entry (i, j) | Row i of A · column j of B |
| Order matters | AB is usually not equal to BA |
| Example | [[1, 2], [3, 4]]·[[5, 6], [7, 8]] = [[19, 22], [43, 50]] |
Worked example
The top-left entry of the example is row 1 of A times column 1 of B: 1·5 + 2·7 = 19. The other entries follow the same pattern.
How to use it in Plotline
- Matrices A and B are filled in and A*B is calculated.
- Change the entries or sizes; type A*B (or A B) and press Enter.
- Try B*A to see that the order changes the answer.
Frequently asked questions
Why do I get “dimensions don’t match”?
The number of columns in the first matrix must equal the number of rows in the second. A 2×3 matrix can multiply a 3×2 matrix, but not a 2×2.
Is it free?
Yes. The matrix calculator is free with no account and no sign-up, and there is no limit on how many matrices you work with. Determinants, inverses, RREF, multiplication and systems of equations are all included, and it works offline once loaded.
Learn more
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Plotline is an independent project and is not affiliated with Desmos, Texas Instruments or Casio.