This paper presents a real-space grid implementation of the Projector Augmented Wave (PAW) method for Density Functional Theory (DFT) calculations. The method uses uniform 3D real-space grids to represent wave functions, densities, and potentials, enabling flexible boundary conditions, efficient multigrid algorithms for solving Poisson and Kohn-Sham equations, and efficient parallelization via domain decomposition. The PAW method is used for all-electron calculations with smooth valence wave functions that can be represented on relatively coarse grids. The accuracy of the method is demonstrated by calculating atomization energies of twenty small molecules and the bulk modulus and lattice constants of bulk aluminum. The method is computationally efficient, comparable to standard plane-wave methods, but requires more memory. The PAW method transforms smooth pseudo wave functions into true all-electron Kohn-Sham wave functions, with core states frozen. The method uses atom-centered all-electron wave functions and projector functions to construct the transformation operator. Smooth core electron densities are constructed, and the pseudo electron density is calculated from wave functions and core densities. The PAW total energy is a function of pseudo wave functions and occupation numbers, with corrections for each atom. The method uses real-space grids for wave functions, densities, and potentials, with integrals converted to sums over grid points. The double grid technique is used to transfer localized functions to real-space grids. The PAW method is implemented with a real-space grid formulation, using discretized forms of densities, potentials, and energies. The pseudo Hartree potential is solved using multigrid techniques, and the total energy is calculated with corrections for each atom. The method is applied to calculate atomization energies of small molecules and the bulk modulus and lattice constants of bulk aluminum. The results show excellent agreement with all-electron calculations, with average and maximum differences of 0.05 eV and 0.15 eV, respectively. The method is also applied to bulk aluminum calculations, showing good agreement with exact all-electron calculations for both the lattice constant and the bulk modulus. The performance of the real-space code is compared to a highly optimized ultra-soft plane-wave code. The real-space code is found to converge faster and requires less memory. The method is efficient for large systems and can take advantage of parallelization and algorithmic improvements. The method is suitable for studying large systems and can be extended to periodic systems using Brillouin zone sampling. The method is also suitable for spin-polarized systems and has been applied to a variety of systems, including small molecules and bulk aluminum. The method is efficient and accurate, with good convergence and performance for large systems.This paper presents a real-space grid implementation of the Projector Augmented Wave (PAW) method for Density Functional Theory (DFT) calculations. The method uses uniform 3D real-space grids to represent wave functions, densities, and potentials, enabling flexible boundary conditions, efficient multigrid algorithms for solving Poisson and Kohn-Sham equations, and efficient parallelization via domain decomposition. The PAW method is used for all-electron calculations with smooth valence wave functions that can be represented on relatively coarse grids. The accuracy of the method is demonstrated by calculating atomization energies of twenty small molecules and the bulk modulus and lattice constants of bulk aluminum. The method is computationally efficient, comparable to standard plane-wave methods, but requires more memory. The PAW method transforms smooth pseudo wave functions into true all-electron Kohn-Sham wave functions, with core states frozen. The method uses atom-centered all-electron wave functions and projector functions to construct the transformation operator. Smooth core electron densities are constructed, and the pseudo electron density is calculated from wave functions and core densities. The PAW total energy is a function of pseudo wave functions and occupation numbers, with corrections for each atom. The method uses real-space grids for wave functions, densities, and potentials, with integrals converted to sums over grid points. The double grid technique is used to transfer localized functions to real-space grids. The PAW method is implemented with a real-space grid formulation, using discretized forms of densities, potentials, and energies. The pseudo Hartree potential is solved using multigrid techniques, and the total energy is calculated with corrections for each atom. The method is applied to calculate atomization energies of small molecules and the bulk modulus and lattice constants of bulk aluminum. The results show excellent agreement with all-electron calculations, with average and maximum differences of 0.05 eV and 0.15 eV, respectively. The method is also applied to bulk aluminum calculations, showing good agreement with exact all-electron calculations for both the lattice constant and the bulk modulus. The performance of the real-space code is compared to a highly optimized ultra-soft plane-wave code. The real-space code is found to converge faster and requires less memory. The method is efficient for large systems and can take advantage of parallelization and algorithmic improvements. The method is suitable for studying large systems and can be extended to periodic systems using Brillouin zone sampling. The method is also suitable for spin-polarized systems and has been applied to a variety of systems, including small molecules and bulk aluminum. The method is efficient and accurate, with good convergence and performance for large systems.