LU Decomposition is also known as LU factorization. Here, 'LU' stands for 'lower upper'. Triangular matrix is a special kind of square matrix. A square matrix is called lower triangular, only when all the entries above the main diagonal are zero. Likewise, square matrix is called upper triangular, only when all the entries below the main diagonal are zero. Use this online matrix solver which helps you to calculate lower triangular matrix (L) and an upper triangular matrix (U) using LU Decomposition method.