The magnetization curves $M(H)$ for ideal type-II superconductors and the maximum, minimum, and saddle-point magnetic fields of the vortex lattice are calculated from Ginzburg-Landau theory for the entire ranges of applied magnetic fields ${H}_{c1}<~H<~{H}_{c2}$ or induction $0<~B<~{\ensuremath{\mu}}_{0}{H}_{c2}$ and Ginzburg-Landau parameters ${2}^{\ensuremath{-}1/2}<~\ensuremath{\kappa}<~1000.$ Results for the triangular and square flux-line lattices are compared with the results of the circular cell approximation. The exact magnetic field $B(x,y)$ and magnetization $M(H,\ensuremath{\kappa})$ are compared with often used approximate expressions, some of which deviate considerably or have limited validity. Useful limiting expressions and analytical interpolation formulas are presented.