The objective of this research was to compare the spray penetration from a common rail injector using equations proposed in the literature to experimentally attained results, using diesel and dimethyl ether (DME) as fuels. The injection occurred in a chamber pressurized with nitrogen at injection pressures of 400 bar and 600 bar into ambient pressures of 12 bar, 16 bar and 18 bar. High speed images were recorded at 10000 fps. Analysis of the results indicated that the models proposed by Wakuri et al. and Sazhin et al., at the same conditions, provided penetration values that were closest to the experimental values. In terms of the two models, it was found that the predicted depth of penetration of diesel fuel was, in general, not very well predicted. The DME showed close correlation with the both models at higher injection pressure and higher chamber pressure. The model proposed by Sazhin appears to produce somewhat better results for DME at the conditions reported in this research. The SMD values of DME were noted to be higher than those of diesel for the same conditions. (C) 2012 Elsevier B.V. All rights reserved.