The determinant of a square matrix (one with the same number of rows and columns) is a calculated quality used to define other properties of that matrix.
(Don’t worry right now about the vague definition; many math professionals would have a hard time doing a better job.)
Calculating the determinant of a 3×3 (or larger) matrix uses the same technique as the 2×2 matrix — take the sum of the products of the down-diagonals () and then subtract the sum of the products of the up-diagonals (/).
Determinant of a 3×3 Matrix
Learn how to calculate the determinant of a 3×3 matrix with this Formula Solver Series tutorial. It even explains the process for any square matrix of 4×4 or larger.