The journal impact factors, published by the Institute for Scientific Information (ISI; Philadelphia, PA), are widely known and are used to evaluate overall journal quality and the quality of the papers published therein. However, when making comparisons between subject fields, the work of individual scientists and their research institutions as reflected in their articles' ISI impact factors can become meaningless. This inequality will remain as long as ISI impact factors are employed as an instrument to assess the quality of international research. Here we propose a new mathematical index entitled Impact Factor Point Average (IFPA) for assessment of the quality of individual research work in different subject fields. The index is established based on a normalization of differences in impact factors, rankings, and number of journal titles in different subject fields. The proposed index is simple and enables the ISI impact factors to be used with equality, especially when evaluating the quality of research work in different subject fields.