Fluxes were determined through the combination of one, two, or three labeling experiments. The 95% CIs were calculated from the flux values using a parameter continuation method described elsewhere (Antoniewicz et al., 2006). The CIs were then compared with the value of their corresponding flux. The number of net fluxes that have CIs that are smaller than the magnitude of the flux are presented along with the SSR and degrees of freedom (i.e. overdetermination). All simulations were based upon the presented model (90 fluxes, including 70 net fluxes and 20 exchange fluxes) and using measurements from C:N 21:1. Nineteen net fluxes, although not constrained, represent fluxes to biomass (e.g. amino acid biosynthetic fluxes to protein) and therefore have smaller measured errors and are established regardless of labeling. Therefore, the number of highly confident fluxes calculated minus the 19 biosynthetic fluxes are shown in parentheses. The number of fluxes determined with high confidence increases with the number of labeling experiments and the degrees of freedom.