The density functional theory full-potential linearized augmented plane wave method with the Generalized Gradient Approximation (PBE-GGA & WC-GGA) and Local Density Approximation for the exchange–correlation potential were applied to calculate the structural and electronic properties of armchair (7, 7) carbon nanotubes. Structural properties such as lattice constants, bulk modules, Young’s modulus, compressibility, bond lengths, muffin-tin radius and effective atomic charge were calculated. According to PBE-GGA, Csingle bondC bond lengths are equal to 1.429 Å and Young’s modulus is equal to 0.930 tetra Pascal being in good agreement with other studies. Band structure, density of states and electronic charge density were calculated. CNTs (7, 7) show a metallic behavior and the electron charge densities of CNTs (7, 7) confirm a covalent bond between two carbon atoms. Moreover, the effects of armchair CNTs chirality on the band gaps and Young’s modulus are illustrated which confirm the calculations.