The present invention relates to a turbidity calibration standard comprising: a number of from 1 to 5 sequentially-interfaced layers, wherein each layer independently comprises a light-permeable polymer or light-permeable interpolymer; a measured light transmission modulating amount of at least one light transmission modulator, which is distributed in any one or more of the layers; and a light-permeable container, which contains the layers and the at least one light transmission modulator. Also, the invention relates to methods of making and using the standard, and kits comprising the standard.