Magnification of ocular lens multiplied by the magnification of the objective
To calculate the total magnification achieved with a compound microscope, the magnification of the ocular lens is multiplied by the magnification of the objective lens. For example, if viewing a sample with the 40x objective, the total magnification would be calculated as follows: a 10X ocular lens used with a 40X objective lens, the total magnification is 400X (10 x 40).