The process of deriving emission-area estimates from Fowler-Nordheim ͑FN͒ plots is investigated, using emission-area extraction functions and an iterative procedure suggested earlier ͓R. G. Forbes, J. Vac. Sci. Technol. B 17, 526 ͑1999͔͒. 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 barrier͒. These have been analyzed using two area-extraction spreadsheets with different models ͑elementary triangular barrier and Schottky-Nordheim barrier͒ 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.