The R factors and the numbers of independent atoms for the entire set of molecular organic structures contained in the Cambridge Structural Database were retrieved and analysed. The average R factor for all structures containing the same number of independent atoms was plotted against the number of independent atoms. A clear correlation was observed. The plot is suggested to give a graphical overview of how values of the R factor for large-molecule structures with 200-1000 independent atoms increase as the number of independent atoms increases. (C) 2000 International Union of Crystallography Printed in Great Britain - all rights reserved.