The charge distribution on the surface of a biased conductive, finite-length, cylindrical nanotube, free standing above an infinite grounded plane, is investigated. The diameter range of the cylinder tube under study is 20–60 nm, which is much larger than the screening length, meaning the quantum and statistical effects on the charge distribution are negligible. The relationship between the charge distribution and the geometry of the nanotube is examined in detail by classical electrostatics using full three-dimensional numerical simulations based on the boundary element method. A model of the concentrated charge at the end of nanotubes is proposed. The charge distribution for a clamped cantilever nanotube is also computed and discussed. The findings here reported are of particular usefulness in the design and modeling of electrostatic actuated nanotube/nanowire based nano-electromechanical systems.