Journal impact factors measure the prestige of journals, not the prestige of researchers.
Researcher productivity can be measured by number of journal articles. Researcher impact can be measured by total number of citations. The h-index (AKA Hirsch index) combines these two factors, simultaneously measuring productivity and impact. An index of h means that your h most highly-cited articles have at least h citations each.
The h-index has been criticized for many reasons, and several alternative indices have been proposed.
Several tools exist for calculating your h-index: