Determinant 3x3 Calculator

Summary

Enter a 3x3 matrix and get the determinant instantly with full cofactor expansion working shown.

How it works

1. Enter the nine elements of your 3x3 matrix into the grid.
2. The calculator expands along the first row using cofactor expansion.
3. Each element in the first row is multiplied by its signed 2x2 minor (cofactor).
4. The three 2x2 minors are each evaluated using the standard ad-bc formula.
5. The three cofactor products are summed to give the final determinant.
6. All intermediate values are shown so you can follow every step.

Use cases

• Verify hand-computed determinants for linear algebra homework.
• Check whether a 3x3 matrix is singular (determinant = 0).
• Understand cofactor expansion step by step while learning.
• Evaluate invertibility before solving a system of linear equations.
• Compute cross-product magnitudes that rely on 3x3 determinants.
• Quickly test multiple matrices when working through exam problems.

Frequently Asked Questions