SOFTSUSY3.3.3 is a program for calculating the spectrum of superparticles in the CP-conserving Minimal Supersymmetric Standard Model (MSSM). It accurately computes the sparticle masses and couplings, incorporating theoretical constraints on soft supersymmetry breaking terms. The program uses weak-scale gauge coupling and fermion mass data, including one-loop finite MSSM corrections, as boundary conditions and ensures successful radiative electroweak symmetry breaking. It also calculates a measure of fine-tuning. The program is designed for easy generalization to extensions of the MSSM and provides a self-contained guide for users, detailing conventions and approximations. The program solves the renormalization group equations with theoretical constraints on soft supersymmetry breaking parameters. It includes a full flavor mixing structure and can calculate the MSSM spectrum, gauge and Yukawa couplings, electroweak symmetry breaking, and fine-tuning. The code is written in object-oriented C++ and can be used with input in the SUSY Les Houches Accord format or via command-line arguments. It is freely available from the SOFTSUSY web-page and can be used for studies of MSSM sparticle searches, as well as other theoretical or astrophysical studies. The program's structure includes detailed descriptions of MSSM parameters, calculation methods, and appendices explaining switches, constants, object structures, and more. It provides a flexible and extendable tool for calculating supersymmetric spectra, with a focus on accuracy and ease of generalization. The code is designed to handle a wide range of input parameters and boundary conditions, including high-scale boundary conditions for soft SUSY breaking parameters. The program is used to calculate the sparticle mass spectrum, gauge and Yukawa couplings, and electroweak symmetry breaking, with a focus on the tree-level and one-loop corrections. The program also includes a fine-tuning calculation to quantify the apparent cancellation of terms in the electroweak symmetry breaking conditions. The code is designed to be user-friendly, with detailed documentation and examples provided for its use.SOFTSUSY3.3.3 is a program for calculating the spectrum of superparticles in the CP-conserving Minimal Supersymmetric Standard Model (MSSM). It accurately computes the sparticle masses and couplings, incorporating theoretical constraints on soft supersymmetry breaking terms. The program uses weak-scale gauge coupling and fermion mass data, including one-loop finite MSSM corrections, as boundary conditions and ensures successful radiative electroweak symmetry breaking. It also calculates a measure of fine-tuning. The program is designed for easy generalization to extensions of the MSSM and provides a self-contained guide for users, detailing conventions and approximations. The program solves the renormalization group equations with theoretical constraints on soft supersymmetry breaking parameters. It includes a full flavor mixing structure and can calculate the MSSM spectrum, gauge and Yukawa couplings, electroweak symmetry breaking, and fine-tuning. The code is written in object-oriented C++ and can be used with input in the SUSY Les Houches Accord format or via command-line arguments. It is freely available from the SOFTSUSY web-page and can be used for studies of MSSM sparticle searches, as well as other theoretical or astrophysical studies. The program's structure includes detailed descriptions of MSSM parameters, calculation methods, and appendices explaining switches, constants, object structures, and more. It provides a flexible and extendable tool for calculating supersymmetric spectra, with a focus on accuracy and ease of generalization. The code is designed to handle a wide range of input parameters and boundary conditions, including high-scale boundary conditions for soft SUSY breaking parameters. The program is used to calculate the sparticle mass spectrum, gauge and Yukawa couplings, and electroweak symmetry breaking, with a focus on the tree-level and one-loop corrections. The program also includes a fine-tuning calculation to quantify the apparent cancellation of terms in the electroweak symmetry breaking conditions. The code is designed to be user-friendly, with detailed documentation and examples provided for its use.