Although a rigorous definition of growth-limiting substrate relies on a kinetic analysis, a simple stoichiometric analysis based on the calculation of the conversion is more applicable. Analysis of single and dual limitations is based on a simulated example for a substrate taken-up by facilitated diffusion (e.g. glucose) or by free diffusion (e.g. ethanol) and shows that a kinetic single or dual limitation can usually be predicted by comparing the conversion of two nutrients with the expected stoichiometry. Stoichiometric analysis of dual limitations is applied to experimental data for Kluyveromyces marxianus (for glucose and oxygen) and Saccharomyces cerevisiae (for glucose and ammonium).