The process of deriving emission-area estimates from Fowler-Nordheim (FN) plots is investigated, using emission-area extraction functions and an iterative procedure suggested earlier [R. G. Forbes, J. Vac. Sci. Technol. B 17, 526 (1999)]. Simulated FN-plot data have been prepared using free-electron theory and three different tunneling-barrier models (elementary triangular barrier, image-rounded "Schottky-Nordheim" barrier, and a quadratically enhanced barrier). These have been analyzed using two area-extraction spreadsheets with different models (elementary triangular barrier and Schottky-Nordheim barrier) embedded in them. It is confirmed that significant errors in the area estimate may occur if the emission model used to analyze the FN-plot data does not correspond well with the model/physics responsible for generating the data. It is also concluded that parameters used in the area-extraction process should correspond to emission variables in the midrange of the FN-plot data. (C) 2004 American Vacuum Society.